What is Basal Metabolic Rate (BMR)?

BMR is the baseline energy expenditure your body requires to maintain life-sustaining functions (organ activity, cellular pumps) while at complete rest and fasted.

How does BMR differ from RMR?

BMR requires strict fasting and rest conditions in a laboratory. Resting Metabolic Rate (RMR) is measured under less restrictive conditions, typically yielding slightly higher results (by 5-10%).

Which BMR formula is the most accurate?

The Mifflin-St Jeor formula is considered the most accurate for modern populations. The Katch-McArdle formula is preferred for athletic individuals with known body fat percentages.

Can I increase my BMR?

Yes. Building skeletal muscle tissue is the most effective way to permanently raise BMR, as muscle requires more resting metabolic maintenance than fat tissue.

Does eating below my BMR slow my metabolism?

Yes. Severe, prolonged caloric restriction below BMR triggers adaptive thermogenesis ("starvation mode"), slowing metabolic rates and signaling muscle breakdown.

How is BMR calculated in metric units?

Mifflin-St Jeor: Men BMR = (10 × kg) + (6.25 × cm) - (5 × age) + 5. Women BMR = (10 × kg) + (6.25 × cm) - (5 × age) - 161.

Does body fat percentage affect BMR?

Yes. Since fat is less metabolically active than muscle, two people of the same weight will have different BMRs if their body fat percentages differ. The Katch-McArdle formula accounts for this.

Does genetics play a role in BMR?

Yes. Genetic variables regulate baseline thyroid output, receptor sensitivity, and body frame size, which account for variations in metabolic rates among individuals.

How does age affect my BMR?

BMR naturally declines by 1-2% per decade after age 30, primarily due to sarcopenia (loss of muscle tissue). Strength training helps preserve muscle mass.

Should I eat fewer calories than my BMR to lose weight?

Generally no. To lose weight safely, set your caloric intake below your TDEE (maintenance level) but above your BMR to protect muscle mass and endocrine function.

health calculator

BMR Calculator

Estimate your basal metabolic rate (BMR) and daily calorie needs at rest based on your age, gender, height, and weight for accurate results.

Basal metabolic rate is the energy your body uses at complete rest. The Mifflin-St Jeor equation gives BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 for men, or − 161 for women. A 30-year-old man, 180 cm, 80 kg, has a BMR of about 1,780 calories per day.

Formula Verified by Dr. Sarah Jenkins, PhD

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Mode

Sex

Ageyears

Heightcm

Weightkg

Body Fat % (optional)%

Activity Level

Results

Mifflin-St Jeor BMR

1,780.0 kcal

Harris-Benedict BMR1,853.6 kcal

Katch-McArdle BMREnter body fat %

Estimated TDEE2,759.0 kcal

Activity Multiplier1.550x

Tip

Save this page to recalculate your metabolism as your weight changes, or to track progress toward a weight goal.

Formula

BMR and TDEE formulas

Mifflin-St Jeor: Men 10w + 6.25h - 5a + 5, Women 10w + 6.25h - 5a - 161 (w=kg, h=cm, a=years). Harris-Benedict and Katch-McArdle formulas shown in Compare Formulas mode. TDEE = BMR × activity factor.

Three formulas are computed together, alongside a calorie-target solver and a weeks-to-goal projection.

Step by step

How the calculation works

1Choose Compare Formulas, Calorie Target, or Time to Goal Weight mode.
2Compare Formulas: enter sex, age, height, weight, and optional body fat % to see Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle plus TDEE.
3Calorie Target: enter your details and a target weekly rate of weight change to get an exact daily calorie target.
4Time to Goal Weight: enter your current and goal weight plus a daily calorie adjustment to see a week-by-week projection.

Related guides

Learn more about this calculation

Guide

BMR and Metabolic Rate: Understanding Your Basal Metabolism

Understand what BMR really measures, how the Mifflin-St Jeor formula works, and how to use BMR and TDEE for practical calorie planning.

Guide

TDEE Calculation Guide: Estimate Maintenance Calories

Learn how TDEE is estimated from BMR and activity, reproduce the calculator result, and validate maintenance calories with real-world trends.

TDEE

TDEE Calculator

Break down Total Daily Energy Expenditure into BMR, activity, and digestion.

Calories

Calorie Calculator

Estimate daily calorie needs for weight loss, maintenance, or muscle gain.

BMI

BMI Calculator

Calculate your Body Mass Index and see your healthy weight range.

Body Composition

Body Fat Calculator

Estimate body fat percentage to use with the Katch-McArdle formula above.

Ideal Weight

Ideal Weight Calculator

Compare six ideal-weight formulas and find your healthy weight range.

Macros

Macro Calculator

Turn your calorie target into daily protein, carb, and fat targets.

health calculator

BMR Calculator

Estimate your basal metabolic rate (BMR) and daily calorie needs at rest based on your age, gender, height, and weight for accurate results.

Formula Verified by Dr. Sarah Jenkins, PhD

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Mode

Sex

Ageyears

Heightcm

Weightkg

Body Fat % (optional)%

Activity Level

Results

Mifflin-St Jeor BMR

1,780.0 kcal

Harris-Benedict BMR1,853.6 kcal

Katch-McArdle BMREnter body fat %

Estimated TDEE2,759.0 kcal

Activity Multiplier1.550x

Tip

Save this page to recalculate your metabolism as your weight changes, or to track progress toward a weight goal.

Summary

Key output metrics

Mifflin-St Jeor

1,780.0 kcal

Most accurate for the general population.

Harris-Benedict

1,853.6 kcal

Revised 1984 formula; tends to run a little higher.

Katch-McArdle

Enter body fat %

Needed to estimate lean mass.

TDEE (Moderate)

2,759.0 kcal

Mifflin-St Jeor BMR × activity factor.

D3 visualization

BMR by formula

Compare Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle (if body fat % is entered).

D3 visualization

TDEE by activity level

Your Mifflin-St Jeor BMR multiplied by each activity tier.

Guide

How to understand and use this calculator

Quick Answer

What is BMR? Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, and body temperature.

The Mifflin-St Jeor equation:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Simple example: a 30-year-old man, 180 cm, 80 kg.

BMR = (10 × 80) + (6.25 × 180) − (5 × 30) + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal/day.

What are your maintenance calories? Maintenance calories = BMR × activity factor. Sedentary ×1.2, Lightly active ×1.375, Moderately active ×1.55.

Key insight: BMR accounts for roughly 60–75% of your total daily calorie burn — it is the foundation everything else builds on.

Use the BMR Calculator

This calculator has three modes, matching the three things people actually need from a BMR tool:

Compare Formulas — enter your sex, age, height, weight, and (optionally) body fat percentage to see Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle side by side, plus your TDEE at your chosen activity level.
Calorie Target — pick a target weekly rate of weight change (losing or gaining), and see the exact daily calorie target, with a safety-floor warning if it drops too low.
Time to Goal Weight — enter your current and goal weight plus a daily calorie adjustment, and see how many weeks it should take, with a week-by-week projection.

Example input (Compare Formulas mode): Male, age 30, height 180 cm, weight 80 kg, no body fat % entered, Moderately Active.

Output: Mifflin-St Jeor = 1,780 kcal/day • Harris-Benedict = 1,853.6 kcal/day • TDEE (Moderately Active, ×1.55) = 2,759 kcal/day.

Example input (Calorie Target mode): Female, age 31, height 168 cm, weight 65 kg, Moderately Active, target rate −1 lb/week.

Output: TDEE = 2,145.2 kcal/day • Daily adjustment = −500 kcal • Target calories = 1,645.2 kcal/day.

What Is BMR?

BMR (Basal Metabolic Rate) is the amount of energy your body needs to maintain its vital functions while at complete rest — no movement, no digestion, just staying alive.

Vital functions BMR covers:

Breathing
Blood circulation
Body temperature regulation
Brain and nerve function
Cell repair and maintenance
Hormone production

Why BMR matters: it is the foundation of your daily calorie needs, it helps you understand your metabolism, and it is essential for weight management and nutrition planning.

The Energy Breakdown of a Day

Your total daily calorie burn splits roughly into three pieces:

BMR (resting): about 60–75% of daily burn — the largest share by far.
Physical activity: roughly 20%, though this varies a lot with lifestyle.
Food digestion (thermic effect of food): roughly 10%.

These are approximate reference bands, not exact formulas — the point is that resting metabolism, not exercise, is what dominates your daily calorie burn for most people.

The Mifflin-St Jeor Equation — Most Accurate Formula

The Mifflin-St Jeor equation, developed in 1990 and validated in multiple studies, is the current clinical standard for estimating BMR in the general population.

The formula:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Step-by-step example: 60-year-old man, 162.56 cm (5'4"), 68.04 kg (150 lb)

Step 1 — convert units: 150 lb ÷ 2.2 = 68.04 kg; 5'4" = 64 in × 2.54 = 162.56 cm.
Step 2 — apply the formula: (10 × 68.04) + (6.25 × 162.56) − (5 × 60) + 5 = 680.4 + 1,016.0 − 300 + 5 = 1,401.4 kcal/day.

Step-by-step example: 25-year-old woman, 172.72 cm (5'8"), 59.87 kg (132 lb)

Step 1 — convert units: 132 lb ÷ 2.2 = 59.87 kg; 5'8" = 68 in × 2.54 = 172.72 cm.
Step 2 — apply the formula: (10 × 59.87) + (6.25 × 172.72) − (5 × 25) − 161 = 598.7 + 1,079.5 − 125 − 161 = 1,392.2 kcal/day.

Why the sex constant differs: men generally carry more fat-free (muscle) mass than women at the same height and weight, and muscle burns more calories at rest than fat — the +5/−161 offset accounts for that average difference.

Comparing BMR Formulas: Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle

Mifflin-St Jeor is not the only validated BMR formula. The Compare Formulas mode above runs three at once:

Mifflin-St Jeor (1990): the current clinical standard, based on modern body composition data. Uses sex, age, height, and weight.
Revised Harris-Benedict (Roza Shizgal, 1984): an update to the original 1918 formula. Tends to run a little higher than Mifflin-St Jeor, especially for people with more body fat.
Katch-McArdle: ignores height, age, and sex entirely and works from lean body mass alone — BMR = 370 + 21.6 × lean mass (kg). Most accurate for people with a known, accurate body fat percentage from the Body Fat Calculator, especially for athletic or muscular individuals.

Worked comparison: 35-year-old female, 165 cm, 70 kg, 25% body fat (52.5 kg lean mass)

Mifflin-St Jeor: (10 × 70) + (6.25 × 165) − (5 × 35) − 161 = 700 + 1,031.25 − 175 − 161 = 1,395.25 kcal/day.
Harris-Benedict: 447.593 + (9.247 × 70) + (3.098 × 165) − (4.330 × 35) = 447.593 + 647.29 + 511.17 − 151.55 = 1,454.5 kcal/day (about 60 kcal higher).
Katch-McArdle: 370 + (21.6 × 52.5) = 370 + 1,134 = 1,504 kcal/day (highest, because it directly credits her lean mass instead of assuming an average body composition for her height and weight).

Worked comparison: 30-year-old male, 180 cm, 80 kg, 18% body fat (65.6 kg lean mass)

Mifflin-St Jeor: 1,780 kcal/day.
Harris-Benedict: 88.362 + (13.397 × 80) + (4.799 × 180) − (5.677 × 30) = 88.362 + 1,071.76 + 863.82 − 170.31 = 1,853.6 kcal/day.
Katch-McArdle: 370 + (21.6 × 65.6) = 370 + 1,417.0 = 1,787.0 kcal/day.

The three formulas rarely agree exactly — treat the spread between them as your realistic margin of error, not a sign that one is "wrong."

From BMR to TDEE: Understanding Daily Calorie Needs

BMR alone is not what you actually burn in a day — Total Daily Energy Expenditure (TDEE) adds your activity level on top.

Formula: TDEE = BMR × Activity Multiplier

Activity multipliers:

Sedentary (little or no exercise): ×1.2
Lightly Active (light exercise 1–3 days/week): ×1.375
Moderately Active (moderate exercise 3–5 days/week): ×1.55
Very Active (hard exercise 6–7 days/week): ×1.725
Extra Active (very hard exercise or physical job): ×1.9

Worked example: BMR = 1,780 kcal/day (30-year-old man, 180 cm, 80 kg)

Sedentary: 1,780 × 1.2 = 2,136 kcal/day
Lightly Active: 1,780 × 1.375 = 2,447.5 kcal/day
Moderately Active: 1,780 × 1.55 = 2,759 kcal/day
Very Active: 1,780 × 1.725 = 3,070.5 kcal/day
Extra Active: 1,780 × 1.9 = 3,382 kcal/day

What your maintenance calories mean: eat at TDEE and your weight stays roughly the same; eat below it and you lose weight; eat above it and you gain weight. For a deeper breakdown of TDEE and its components, see the TDEE Calculator.

Solving Backward: Finding Your Calorie Target for a Weight Goal

Most BMR tools stop at TDEE. The Calorie Target mode solves the next question directly: how many calories should you actually eat to hit a specific weekly rate of weight change? Once you have a target, the Calorie Calculator can help translate it into a full daily eating plan.

Formula: Target calories = TDEE + (target weekly rate in lb × 3,500 ÷ 7)

This uses the common approximation that one pound of body weight is roughly equivalent to 3,500 kcal — a useful planning estimate, not an exact biological constant.

Worked example: 31-year-old female, 168 cm, 65 kg, Moderately Active, target rate −1 lb/week.

TDEE = 1,384 × 1.55 = 2,145.2 kcal/day.
Daily adjustment = −1 × 3,500 ÷ 7 = −500 kcal/day.
Target calories = 2,145.2 − 500 = 1,645.2 kcal/day.

The calculator checks this target against a safety floor — under about 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision — and flags it if your target dips below that line.

Projecting Time to Reach a Goal Weight

The Time to Goal Weight mode answers a different question: given a chosen daily calorie deficit or surplus, how long will it realistically take to reach a target weight?

Formula: Weeks to goal = |goal weight − current weight| (in lb) × 3,500 ÷ |daily calorie adjustment| ÷ 7

Worked example: current weight 65 kg, goal weight 58 kg (a 7 kg / 15.4 lb loss), daily deficit −500 kcal/day.

Total energy needed: 15.4 lb × 3,500 = 53,900 kcal.
Days to goal: 53,900 ÷ 500 ≈ 108 days.
Weeks to goal: 108 ÷ 7 ≈ 15.4 weeks (about 3.5 months).

This is a straight-line estimate — real weight loss and gain are rarely perfectly linear, since water weight, muscle adaptation, and metabolic adjustment all play a role. Treat the projection as a planning estimate, not a guarantee.

BMR vs. RMR — What's the Difference?

BMR (Basal Metabolic Rate): measured under strict laboratory conditions — complete rest, a temperate environment, and a 12-hour fast. Excludes digestion entirely.

RMR (Resting Metabolic Rate): measured under less strict conditions, at any time of day, and includes some digestive energy cost. RMR typically runs about 10% higher than BMR for the same person.

Formula used: BMR calculators (including this one) use Mifflin-St Jeor. RMR is often estimated with a modified Harris-Benedict approach instead.

For practical, everyday purposes most people use BMR and RMR interchangeably — the difference is small enough that it rarely changes a nutrition plan.

Factors Affecting BMR

What raises or lowers BMR:

Muscle mass — increases BMR; muscle burns roughly three times as many calories at rest as fat tissue.
Age — BMR typically declines 1–2% per decade after early adulthood, mostly from age-related muscle loss (sarcopenia), which strength training can slow.
Sex — men generally have higher BMR due to greater average muscle mass.
Body weight — more total cells generally means more baseline energy demand.
Genetics — individual variation in thyroid output and cellular efficiency.
Hormones — thyroid hormones (T3/T4) are the master regulators; hyperthyroidism raises BMR, hypothyroidism lowers it.
Body temperature and environment — fever and cold exposure both increase BMR as the body works harder to regulate temperature.
Pregnancy — increases BMR to support fetal development.

What you can influence: muscle mass through strength training, body weight through diet and exercise, and to a small extent, environmental exposure.

What you cannot control: age, genetics, and sex.

How to Calculate BMR in Excel

Every formula on this page is a one-line spreadsheet formula. Put weight (kg) in B1, height (cm) in B2, age in B3, and sex ("M"/"F") in B4.

Mifflin-St Jeor: =IF(B4="M", 10*B1+6.25*B2-5*B3+5, 10*B1+6.25*B2-5*B3-161)

Harris-Benedict (revised): =IF(B4="M", 88.362+13.397*B1+4.799*B2-5.677*B3, 447.593+9.247*B1+3.098*B2-4.330*B3)

Katch-McArdle (lean mass in kg in B5): =370+21.6*B5

TDEE (BMR in B6, activity multiplier in B7): =B6*B7

Target calories for a weekly rate (weekly lb change in B8): =B6*B7+(B8*3500/7)

Weeks to reach a goal weight (weight difference in lb in B9, daily adjustment in kcal in B10): =ABS(B9)*3500/ABS(B10)/7

Pounds to kilograms: =B_lb/2.2046226218 • Feet/inches to centimeters: =(feet*12+inches)*2.54

Real-World BMR Examples

Example 1 — 40-year-old man, 85 kg, 175 cm: BMR = (10 × 85) + (6.25 × 175) − (5 × 40) + 5 = 850 + 1,093.75 − 200 + 5 = 1,748.75 kcal/day.

Example 2 — 28-year-old woman, 60 kg, 165 cm: BMR = (10 × 60) + (6.25 × 165) − (5 × 28) − 161 = 600 + 1,031.25 − 140 − 161 = 1,330.25 kcal/day.

Example 3 — Sedentary office worker vs. active tradesperson, same BMR of 1,600 kcal/day: Sedentary TDEE = 1,600 × 1.2 = 1,920 kcal/day. Very Active TDEE = 1,600 × 1.725 = 2,760 kcal/day — an 840 kcal/day gap from activity level alone, roughly the same size as the entire BMR difference between two different-sized people.

Example 4 — Weight-loss deficit sanity check: BMR 1,500 kcal/day, Lightly Active (×1.375) → TDEE = 2,062.5 kcal/day. Eating 300–500 kcal below that means a target range of about 1,562.5–1,762.5 kcal/day, for an estimated loss of roughly 0.6–1.0 lb/week using the 3,500-kcal-per-pound approximation — noticeably slower than the "1–2 lbs/week" some sources casually quote for the same deficit.

Practice Problems

Problem 1: Calculate the BMR for a 40-year-old man who weighs 85 kg and is 175 cm tall. Solution: (10 × 85) + (6.25 × 175) − (5 × 40) + 5 = 850 + 1,093.75 − 200 + 5 = 1,748.75 kcal/day.

Problem 2: Calculate the BMR for a 28-year-old woman who weighs 60 kg and is 165 cm tall. Solution: (10 × 60) + (6.25 × 165) − (5 × 28) − 161 = 600 + 1,031.25 − 140 − 161 = 1,330.25 kcal/day.

Problem 3: A person has a BMR of 1,500 kcal and is Moderately Active (×1.55). What are their maintenance calories? Solution: 1,500 × 1.55 = 2,325 kcal/day.

Problem 4: A person has a BMR of 1,600 kcal and is Sedentary (×1.2). What are their maintenance calories? Solution: 1,600 × 1.2 = 1,920 kcal/day.

Problem 5: A 35-year-old woman weighs 70 kg and is 168 cm tall. Calculate her BMR. Solution: (10 × 70) + (6.25 × 168) − (5 × 35) − 161 = 700 + 1,050 − 175 − 161 = 1,414 kcal/day.

Answers: 1) 1,748.75 kcal/day — 2) 1,330.25 kcal/day — 3) 2,325 kcal/day — 4) 1,920 kcal/day — 5) 1,414 kcal/day.

Common BMR Mistakes

Using the wrong formula for your sex. Mistake: applying the male constant to a female height/weight or vice versa. Fix: always confirm the sex-specific constant (+5 for men, −161 for women) before calculating by hand.
Forgetting to convert units. Mistake: plugging pounds or feet/inches directly into a formula built for kilograms and centimeters. Fix: convert first — divide pounds by 2.2046226218 for kg, multiply total inches by 2.54 for cm.
Treating BMR as your total daily calorie budget. Mistake: eating only your BMR number and wondering why you feel exhausted. Fix: multiply BMR by an activity factor to get TDEE — that is your real daily target.
Ignoring activity level entirely. Mistake: assuming BMR = daily burn regardless of how active you are. Fix: pick the activity tier that honestly matches your week, not your goal.
Ignoring body composition. Mistake: comparing two people's BMR by weight alone. Fix: if you know your body fat percentage, cross-check with Katch-McArdle in Compare Formulas mode, or compare against your Ideal Weight Calculator range.
Using stale numbers. Mistake: recalculating a diet plan around a BMR from months ago. Fix: recalculate whenever your weight changes meaningfully.
Chasing an aggressive deficit. Mistake: assuming a bigger calorie cut means faster, safer results. Fix: use the Calorie Target mode's safety-floor warning — going too far below BMR risks muscle loss and metabolic slowdown.
Skipping medical guidance. Mistake: making significant diet changes from a calculator alone. Fix: use these numbers as a starting point for a conversation with a doctor or registered dietitian, especially for aggressive goals.

What This Calculator Can and Cannot Do

This calculator CAN help with:

Estimating BMR using three validated formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle)
Finding your TDEE (maintenance calories) at any activity level
Solving backward for the calorie target that hits a weekly weight-change goal
Projecting how many weeks it should take to reach a goal weight
Flagging calorie targets that fall below a common safety floor

This calculator CANNOT do:

Measure your BMR exactly — indirect calorimetry is the only way to do that
Account for individual metabolic adaptation over long diets
Provide personalized medical or nutrition advice
Calculate BMR reliably for children under 18
Account for pregnancy or specific medical conditions
Guarantee a specific weight-loss or weight-gain timeline — the projection is a planning estimate, not a promise

Final Summary

A BMR calculator is the starting point for almost every calorie or weight-management decision — everything from TDEE to a deficit target builds on it. Compare formulas when you want a sanity check, solve backward for a calorie target when you have a weekly goal, and project a timeline when you want to know how long a goal will realistically take.

Remember the key formulas:

BMR (men): (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
BMR (women): (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
TDEE: BMR × activity multiplier
Calorie target: TDEE + (weekly rate in lb × 3,500 ÷ 7)

Quick reference (activity multipliers): Sedentary ×1.2 • Lightly Active ×1.375 • Moderately Active ×1.55 • Very Active ×1.725 • Extra Active ×1.9.

Start now — enter your details above to see your BMR, TDEE, and a personalized plan across all three modes, completely free.

Related concepts

Mifflin-St Jeor Equation

The current clinical standard for estimating BMR from weight, height, age, and sex.

Total Daily Energy Expenditure (TDEE)

BMR multiplied by an activity factor — your real daily calorie maintenance number.

Katch-McArdle Equation

A lean-mass-based BMR formula, most accurate for people with a known, accurate body fat percentage.

Adaptive Thermogenesis

The metabolic slowdown the body triggers during prolonged, severe calorie restriction.

Frequently Asked Questions

What is a BMR calculator?+

A BMR calculator estimates your basal metabolic rate — the calories your body burns at complete rest — most commonly using the Mifflin-St Jeor equation.

What is BMR?+

BMR (Basal Metabolic Rate) is the number of calories your body burns at rest to maintain vital functions like breathing, circulation, and body temperature regulation.

How do I calculate my BMR?+

Use the Mifflin-St Jeor equation: for men, (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5; for women, the same but − 161 instead of + 5. Or enter your details into the calculator above.

What are my maintenance calories?+

Maintenance calories equal your TDEE — BMR multiplied by your activity factor. Use the Compare Formulas mode above to see it at any activity level.

What is the Mifflin-St Jeor equation?+

The Mifflin-St Jeor equation, developed in 1990, is the current clinical standard for estimating BMR from weight, height, age, and sex.

Which BMR formula is most accurate?+

Mifflin-St Jeor is considered most accurate for the general population. Katch-McArdle is more accurate if you know your body fat percentage, since it accounts for lean mass directly.

What is the difference between BMR and TDEE?+

BMR is the calories burned at complete rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by your activity level, plus the small additional cost of digesting food.

What is the difference between BMR and RMR?+

BMR is measured under strict lab conditions (complete rest, 12-hour fast). RMR is measured less strictly and runs about 10% higher because it includes some digestive cost.

How accurate is a BMR calculator?+

Mifflin-St Jeor typically has a margin of error of about 5-10% compared to lab-measured BMR (indirect calorimetry), which makes it a strong estimate but not an exact measurement.

Can I use BMR for weight loss?+

Yes. Calculate your TDEE (BMR × activity factor), then use the Calorie Target mode to find a calorie target 300-500 kcal below TDEE for a sustainable weekly loss.

How much weight can I safely lose per week?+

A deficit of 300-500 kcal/day works out to roughly 0.6-1.0 lb/week using the 3,500-kcal-per-pound approximation. Faster loss usually means an unsustainably large deficit.

Is it safe to eat below my BMR?+

Eating below BMR for extended periods can trigger metabolic slowdown and muscle loss. Most guidance recommends staying above roughly 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision.

Does muscle mass affect BMR?+

Yes — muscle tissue burns significantly more calories at rest than fat tissue, so more lean mass means a higher BMR. This is why Katch-McArdle, which uses lean mass directly, can be more accurate for muscular individuals.

Is this BMR calculator free?+

Yes — completely free, with no registration required.

Formula

BMR and TDEE formulas

Mifflin-St Jeor: Men 10w + 6.25h - 5a + 5, Women 10w + 6.25h - 5a - 161 (w=kg, h=cm, a=years). Harris-Benedict and Katch-McArdle formulas shown in Compare Formulas mode. TDEE = BMR × activity factor.

Three formulas are computed together, alongside a calorie-target solver and a weeks-to-goal projection.

Step by step

How the calculation works

1Choose Compare Formulas, Calorie Target, or Time to Goal Weight mode.
2Compare Formulas: enter sex, age, height, weight, and optional body fat % to see Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle plus TDEE.
3Calorie Target: enter your details and a target weekly rate of weight change to get an exact daily calorie target.
4Time to Goal Weight: enter your current and goal weight plus a daily calorie adjustment to see a week-by-week projection.

Related guides

Learn more about this calculation

Guide

BMR Calculator

Inputs

Results

BMR and TDEE formulas

How the calculation works

Learn more about this calculation

BMR and Metabolic Rate: Understanding Your Basal Metabolism

TDEE Calculation Guide: Estimate Maintenance Calories

TDEE Calculator

Calorie Calculator

BMI Calculator

Body Fat Calculator

Ideal Weight Calculator

Macro Calculator

Sources & methodology

BMR Calculator

Inputs

Results

Key output metrics

BMR by formula

TDEE by activity level

How to understand and use this calculator

Quick Answer

Use the BMR Calculator

What Is BMR?

The Energy Breakdown of a Day

The Mifflin-St Jeor Equation — Most Accurate Formula

Comparing BMR Formulas: Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle

From BMR to TDEE: Understanding Daily Calorie Needs

Solving Backward: Finding Your Calorie Target for a Weight Goal

Projecting Time to Reach a Goal Weight

BMR vs. RMR — What's the Difference?

Factors Affecting BMR

How to Calculate BMR in Excel

Real-World BMR Examples

Practice Problems

Common BMR Mistakes

What This Calculator Can and Cannot Do

Final Summary

Related concepts

Frequently Asked Questions

BMR and TDEE formulas

How the calculation works

Learn more about this calculation

BMR and Metabolic Rate: Understanding Your Basal Metabolism

TDEE Calculation Guide: Estimate Maintenance Calories

TDEE Calculator

Calorie Calculator

BMI Calculator

Body Fat Calculator

Ideal Weight Calculator

Macro Calculator

Sources & methodology

Key output metrics

BMR by formula

TDEE by activity level

How to understand and use this calculator

Quick Answer

Use the BMR Calculator

What Is BMR?

The Energy Breakdown of a Day

The Mifflin-St Jeor Equation — Most Accurate Formula

Comparing BMR Formulas: Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle

From BMR to TDEE: Understanding Daily Calorie Needs

Solving Backward: Finding Your Calorie Target for a Weight Goal

Projecting Time to Reach a Goal Weight

BMR vs. RMR — What's the Difference?

Factors Affecting BMR

How to Calculate BMR in Excel

Real-World BMR Examples

Practice Problems

Common BMR Mistakes

What This Calculator Can and Cannot Do

Final Summary

Related concepts

Frequently Asked Questions