health calculator

One-Rep Max (1RM) Calculator

Estimate your one-rep max from a real working set using the Epley and Brzycki formulas, plus a training percentage table.

Two regression formulas estimate 1RM from a lighter set: Epley = Weight × (1 + Reps ÷ 30), and Brzycki = Weight × 36 ÷ (37 − Reps). Lifting 100 kg for 5 reps gives an Epley estimate of 116.7 kg and a Brzycki estimate of 112.5 kg — both formulas are most reliable in the 1-5 rep range.

Formula Verified by Dr. Sarah Jenkins, PhD

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

Saved Runs

Inputs

Weight lifted

Reps performed

Results

Average Estimated 1RM

114.6

Epley Formula116.7

Brzycki Formula112.5

Training Percentage Table

95%108.9

90%103.1

85%97.4

80%91.7

75%85.9

70%80.2

65%74.5

60%68.8

55%63

50%57.3

Tip

Save this page to plan training percentages, track strength progress over time, or estimate a 1RM without testing it directly.

Formula

Epley and Brzycki 1RM formulas

Epley: 1RM = Weight × (1 + Reps ÷ 30). Brzycki: 1RM = Weight × 36 ÷ (37 − Reps).

Both are regression fits from real lifting data, most reliable in the 1-5 rep range and progressively less reliable above 8-10 reps.

Step by step

How the calculation works

1Enter the weight and number of reps from a real working set (ideally 1-8 reps, taken close to failure with good form).
2Compare the Epley and Brzycki estimates — a wide gap between them is a signal the rep count was too high for a reliable estimate.
3Use the training percentage table to plan working weights for future sessions.
4Re-estimate every few weeks as your strength changes, rather than testing a true 1RM too frequently.

Example

Worked example: 100 kg × 5 reps

Epley: 100 × (1 + 5÷30) = 116.7 kg. Brzycki: 100 × 36 ÷ (37−5) = 112.5 kg. The two are within about 4 kg of each other, a tight spread expected at 5 reps.

Related guides

Learn more about this calculation

Guide

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Learn the fastest reliable workflow for using Do The Calculation calculators, reading results, checking formulas, and using save, print, share, and export actions correctly.

Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

Understand how Do The Calculation formulas are presented, what the explanation blocks mean, and how to verify calculator logic before using a result in a real decision.

One-Rep Max (1RM) Calculator

Estimate your one-rep max from a real working set using the Epley and Brzycki formulas, plus a training percentage table.

Formula Verified by Dr. Sarah Jenkins, PhD

How to understand and use this calculator

Two formulas, because no single one is exactly right

A one-rep max (1RM) is the heaviest weight you could lift for a single complete repetition with good form. Testing it directly is fatiguing and carries injury risk, so most lifters estimate it from a lighter, higher-rep set instead. The two most widely used formulas are Epley — 1RM = Weight × (1 + Reps ÷ 30) — and Brzycki — 1RM = Weight × 36 ÷ (37 − Reps). Both are regression fits built from real lifting data, not derived from a single physical law, which is exactly why they don't always agree: Epley (published by Boyd Epley in 1985) tends to estimate slightly higher at higher rep counts, while Brzycki (Matt Brzycki, 1993) tends to run slightly lower.

Where each formula is more reliable

In the 1-to-5 rep range, Epley and Brzycki agree closely, and both are fairly accurate — fatigue hasn't had much chance to distort the relationship between weight and reps yet. Above about 8-10 reps, the two formulas diverge more, and both lose accuracy, because endurance and muscular fatigue start to matter as much as raw strength. This calculator shows both formulas together specifically so a large gap between them is visible as a signal — a wide spread usually means the set used to estimate from had too many reps for a reliable 1RM projection.

Why a percentage table matters more than the single 1RM number

Most strength programs aren't written around your exact 1RM in isolation — they're written as a percentage of it ("work up to a set of 5 at 75% of 1RM"). That's because training at a fixed percentage keeps intensity comparable across lifters and across time as your 1RM changes, without needing the coach to recalculate absolute weights for every person. The percentage table below converts your estimated 1RM into the working weights coaches commonly program against — from heavy singles and doubles near 90-95% down to higher-volume, lower-intensity work around 50-60%.

Worked example: a low-rep set (most reliable range)

Lifting 100 kg for 5 reps: Epley estimates 100 × (1 + 5÷30) = 116.7 kg. Brzycki estimates 100 × 36 ÷ (37−5) = 112.5 kg. The two are within about 4 kg of each other — a tight spread, which is expected at 5 reps and suggests both estimates are reasonably trustworthy here.

Worked example: a higher-rep set (less reliable range)

Lifting 225 lb for 8 reps: Epley estimates 225 × (1 + 8÷30) = 285.0 lb. Brzycki estimates 225 × 36 ÷ (37−8) = 279.3 lb. The gap widens to almost 6 lb even though the weight only went up — at 8 reps, fatigue is playing a bigger role, and by 10+ reps the spread between formulas (and their real-world accuracy) gets noticeably worse. Averaging the two here gives a reasonable middle estimate of about 282 lb, but treat any estimate from a set over 8-10 reps as a rougher approximation than one from a 3-5 rep set.

Related calculators

Turning your 1RM into a full training week? The Workout Calculator helps structure sets and volume around it. Strength training also runs on recovery and fuel — check the TDEE Calculator for total daily energy needs and the Macro Calculator for a protein/carb/fat split that supports the training this 1RM feeds into. Once you have a solid 1RM estimate, see how it stacks up against typical lifters with the Bench Press Standards Calculator or the Squat Deadlift Standards Calculator. For bodyweight-only muscular-endurance benchmarks, the Push-Up Sit-Up Fitness Test Calculator covers the equipment-free side of the same strength picture.

Related concepts

1RM (One-Rep Max)

The maximum weight liftable for exactly one complete repetition with proper form.

Epley formula

1RM = Weight × (1 + Reps ÷ 30) — a regression-based 1RM estimate published by Boyd Epley in 1985.

Brzycki formula

1RM = Weight × 36 ÷ (37 − Reps) — a regression-based 1RM estimate from Matt Brzycki, 1993.

Training percentage

A working weight expressed as a percentage of 1RM, used to program intensity consistently across a training cycle.

Frequently Asked Questions

What is a one-rep max (1RM)?+

The maximum weight you could lift for exactly one complete repetition with proper form. It's a common benchmark for strength training programs, which are often written as a percentage of 1RM.

What's the formula for estimating 1RM?+

Two common formulas: Epley = Weight × (1 + Reps ÷ 30), and Brzycki = Weight × 36 ÷ (37 − Reps). They're both regression fits from real lifting data and typically agree closely for sets of 5 reps or fewer.

Which formula is more accurate, Epley or Brzycki?+

Neither is universally more accurate. Brzycki tends to fit slightly better at low rep counts (2-6), Epley tends to fit slightly better at higher rep counts (7-10+), and both lose reliability past about 10 reps.

Is it safer to estimate 1RM than to test it directly?+

Generally yes for most lifters — a true 1RM attempt carries more injury risk and fatigue than working from a submaximal set. Estimating from a 3-5 rep set at good form is the more common approach outside of competitive powerlifting testing.

Why do the two formulas give different numbers for the same set?+

Because they're independently fit regression equations, not exact physical formulas — a wider gap between them (especially at higher rep counts) is itself a signal that the estimate is less reliable.

How often should I retest my 1RM?+

Most lifting programs re-estimate every 4-12 weeks, since testing too often adds fatigue without giving strength enough time to actually change.

Can beginners use an estimated 1RM to plan training?+

Yes, though beginner strength changes quickly, so an estimated 1RM from a few weeks ago may already be outdated — beginners typically re-estimate more often than advanced lifters.

Does this work for any exercise, not just bench, squat, and deadlift?+

The formulas are general and work for any single-joint or compound lift, though they were originally validated primarily on major compound barbell lifts, where they're most commonly used and trusted.

How the calculation works

1Enter the weight and number of reps from a real working set (ideally 1-8 reps, taken close to failure with good form).

2Compare the Epley and Brzycki estimates — a wide gap between them is a signal the rep count was too high for a reliable estimate.

3Use the training percentage table to plan working weights for future sessions.

4Re-estimate every few weeks as your strength changes, rather than testing a true 1RM too frequently.

How to understand and use this calculator

Two formulas, because no single one is exactly right

Where each formula is more reliable

Why a percentage table matters more than the single 1RM number

Worked example: a low-rep set (most reliable range)

Worked example: a higher-rep set (less reliable range)

Related calculators

Related concepts

1RM (One-Rep Max)

The maximum weight liftable for exactly one complete repetition with proper form.

Epley formula

1RM = Weight × (1 + Reps ÷ 30) — a regression-based 1RM estimate published by Boyd Epley in 1985.

Brzycki formula

1RM = Weight × 36 ÷ (37 − Reps) — a regression-based 1RM estimate from Matt Brzycki, 1993.

Training percentage

A working weight expressed as a percentage of 1RM, used to program intensity consistently across a training cycle.

Frequently Asked Questions

What is a one-rep max (1RM)?+

The maximum weight you could lift for exactly one complete repetition with proper form. It's a common benchmark for strength training programs, which are often written as a percentage of 1RM.

What's the formula for estimating 1RM?+

Which formula is more accurate, Epley or Brzycki?+

Is it safer to estimate 1RM than to test it directly?+

Why do the two formulas give different numbers for the same set?+

How often should I retest my 1RM?+

Most lifting programs re-estimate every 4-12 weeks, since testing too often adds fatigue without giving strength enough time to actually change.

Can beginners use an estimated 1RM to plan training?+

Yes, though beginner strength changes quickly, so an estimated 1RM from a few weeks ago may already be outdated — beginners typically re-estimate more often than advanced lifters.

Does this work for any exercise, not just bench, squat, and deadlift?+

The formulas are general and work for any single-joint or compound lift, though they were originally validated primarily on major compound barbell lifts, where they're most commonly used and trusted.

One-Rep Max (1RM) Calculator

Inputs

Results

Epley and Brzycki 1RM formulas

How the calculation works

Worked example: 100 kg × 5 reps

Learn more about this calculation

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

One-Rep Max (1RM) Calculator

Inputs

Results

Key output metrics

Training Percentage Table

How to understand and use this calculator

Two formulas, because no single one is exactly right

Where each formula is more reliable

Why a percentage table matters more than the single 1RM number

Worked example: a low-rep set (most reliable range)

Worked example: a higher-rep set (less reliable range)

Related calculators

Related concepts

Frequently Asked Questions

Epley and Brzycki 1RM formulas

How the calculation works

Worked example: 100 kg × 5 reps

Learn more about this calculation

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

Key output metrics

Training Percentage Table

How to understand and use this calculator

Two formulas, because no single one is exactly right

Where each formula is more reliable

Why a percentage table matters more than the single 1RM number

Worked example: a low-rep set (most reliable range)

Worked example: a higher-rep set (less reliable range)

Related calculators

Related concepts

Frequently Asked Questions