health calculator

BAC Calculator

Estimate your blood alcohol concentration (BAC) based on drinks consumed, body weight, gender, and time elapsed since drinking.

Formula Verified by Dr. Sarah Jenkins, PhD

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

Saved Runs

Inputs

Gender

Standard drinksdrinks

Weight (lbs)lbs

Time elapsed (hours)hours

Results

Estimated BAC %

0.049%

Safety StatusSome Alcohol Effects (> 0%)

Drinks Consumed3 standard drinks

Time Elapsed2 hours

Tip

Save this calculator to quickly reference blood alcohol estimates and sober timeline profiles.

Formula

Widmark BAC formula

BAC % = (A × 5.14 / (W × r)) - 0.015 × H

A = liquid ounces of pure alcohol. W = weight in lbs. r = gender rate (0.73 male, 0.66 female). H = hours.

Step by step

How the calculation works

1Enter the number of standard drinks consumed (1 drink = 12oz of 5% beer, 5oz of 12% wine, or 1.5oz of 40% spirits).
2Provide your body weight in pounds.
3Choose your gender (determines body water absorption constants).
4Specify elapsed hours since the first drink to account for metabolism.

Example

Example BAC estimate

A 160 lb male who has had 3 standard drinks over 2 hours has an estimated current BAC of about 0.049%, below the 0.08% legal driving limit but still showing measurable impairment.

Related guides

Learn more about this calculation

Guide

BAC Estimation Guide: Formula, Limits, and Safety

Learn how BAC estimates work, what the DTC calculator assumes, why results vary, and why no estimate can tell you when it is safe to drive.

Site 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.

Sources & methodology

This calculator implements published formulas. Each source below is the primary reference for a specific part of the calculation, so you can verify the result independently.

GovernmentDrinking Levels and Patterns Defined (standard drink definition)

National Institute on Alcohol Abuse and Alcoholism (NIH)

Definition of a US standard drink as 14 grams of pure alcohol, used to convert drink counts before applying the Widmark formula.

Read how we select formulas, review calculations, and handle corrections in our methodology. Found an error? Tell us and we will correct it and note the change.

How to understand and use this calculator

How Blood Alcohol Concentration (BAC) is Estimated

Blood Alcohol Concentration (BAC) measures the percentage of alcohol present in an individual’s bloodstream. It is expressed as a mass of alcohol per volume of blood (e.g., 0.08% means 0.08 grams of alcohol per 100 mL of blood).

Clinical estimation of BAC is typically computed using the Widmark Formula, developed by Swedish physician Erik M. P. Widmark. The formula calculates the peak BAC by distributing consumed alcohol mass throughout body water (scaled by body weight and a gender-specific gender distribution ratio), and then subtracts alcohol metabolized by the liver over elapsed time.

The Mathematics of the Widmark BAC Formula

The simplified Widmark formula used to estimate BAC is:

BAC % = ( (A × 5.14)/(W × r) ) - β × H

Where:

* A is the total liquid ounces of pure alcohol consumed (e.g., a 12 oz beer at 5% alcohol contains 12 × 0.05 = 0.60 oz of pure alcohol).

* W is the individual’s body weight in pounds.

* r is the gender-specific alcohol distribution ratio (average of 0.73 for males and 0.66 for females to account for differences in body fat and water content).

* β is the metabolic elimination rate per hour, standardized at 0.015% per hour for most healthy adults.

* H is the total elapsed time in hours since the first drink was consumed.

Alcohol Metabolism and Safety Realities

The human liver metabolizes alcohol at a constant average rate of approximately 0.015% BAC reduction per hour. This rate cannot be accelerated by drinking coffee, taking cold showers, exercising, or sleeping. The only factor that reduces BAC is time.

A BAC of 0.08% or higher is the legal limit for driving in most U.S. states and countries, representing significant cognitive and motor impairment. However, lower levels (0.05%) also carry measurable impairment and increase accident risks.

How to Use This Calculator

Select your gender, enter the number of standard drinks consumed, your body weight in pounds, and the hours elapsed since your first drink.

The calculator converts drinks to ounces of pure alcohol, applies the Widmark formula to find your peak BAC, then subtracts the standard 0.015%-per-hour metabolic elimination rate for the elapsed time to estimate your current BAC.

Worked Example: 3 Drinks, 160 lb Male, 2 Hours Elapsed

3 standard drinks (1.8 oz pure alcohol), 160 lb male, 2 hours since the first drink.

Peak BAC: (1.8 × 5.14) / (160 × 0.73) ≈ 0.079%.

Current BAC after 2 hours of elimination: 0.079% - (0.015 × 2) ≈ 0.049% — below the 0.08% legal driving limit, but still in the "Impairment Detected" range above 0.05%.

Time to reach 0.00% BAC from the peak: 0.079 / 0.015 ≈ 5.3 hours.

Related Calculators

Pair this with the TDEE calculator to see how alcohol calories fit your daily energy budget, or the water intake calculator for rehydration guidance. Not sure how many standard drinks a specific beer, wine, or spirit pour actually contains? The Alcohol Unit Calculator converts any volume and ABV into US standard drinks and UK units before you estimate BAC here.

Related concepts

Widmark Formula

The clinical mathematical equation used to estimate BAC based on weight, sex, and alcohol consumption.

Standard Drink

A unit of alcohol measure containing 14 grams of pure ethanol.

Metabolic Elimination Rate

The rate at which the body processes and breaks down alcohol, typically 0.015% per hour.

Frequently Asked Questions

What is BAC?+

Blood Alcohol Concentration (BAC) is the metric used to measure the amount of alcohol in a person's bloodstream, expressed as a percentage.

What is the legal driving limit for BAC?+

In the United States and many other countries, the legal limit for driving is a BAC of 0.08%. In some regions, the limit is lower at 0.05% or zero.

How fast does the body metabolize alcohol?+

The body metabolizes alcohol at a constant rate of approximately 0.015% BAC reduction per hour. This rate cannot be sped up.

How much alcohol is in a standard drink?+

A standard drink in the US contains about 0.6 ounces (14 grams) of pure alcohol, which corresponds to 12 oz of standard beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV).

Why does BAC differ by gender?+

Men generally have higher water content and lower body fat percentages than women of equal weight, which dilutes alcohol more effectively and results in a lower BAC for the same intake.

Can drinking coffee or taking a cold shower lower my BAC?+

No. Coffee and cold showers may make you feel more awake, but they have zero effect on the rate at which your liver metabolizes alcohol.

How accurate is this BAC calculator?+

This calculator is a mathematical estimate based on average metabolic rates and the Widmark formula. Individual BAC values vary based on genetics, food intake, hydration, and medication.

Does food affect BAC?+

Drinking on an empty stomach causes alcohol to absorb more rapidly, leading to a higher and faster peak BAC. Food slows absorption but does not prevent alcohol from entering the bloodstream.

What is the Widmark formula?+

The Widmark formula is a clinical mathematical model used to estimate blood alcohol concentration based on body weight, biological sex, alcohol volume consumed, and time elapsed.

How long does it take to sober up completely?+

It depends on your peak BAC. Divide your peak BAC by the metabolic rate of 0.015% per hour to find the approximate number of hours required to reach 0.00%.

Sources & methodology

This calculator implements published formulas. Each source below is the primary reference for a specific part of the calculation, so you can verify the result independently.

GovernmentDrinking Levels and Patterns Defined (standard drink definition)

National Institute on Alcohol Abuse and Alcoholism (NIH)

Definition of a US standard drink as 14 grams of pure alcohol, used to convert drink counts before applying the Widmark formula.

Read how we select formulas, review calculations, and handle corrections in our methodology. Found an error? Tell us and we will correct it and note the change.

How to understand and use this calculator

How Blood Alcohol Concentration (BAC) is Estimated

The Mathematics of the Widmark BAC Formula

The simplified Widmark formula used to estimate BAC is:

BAC % = ( (A × 5.14)/(W × r) ) - β × H

Where:

* A is the total liquid ounces of pure alcohol consumed (e.g., a 12 oz beer at 5% alcohol contains 12 × 0.05 = 0.60 oz of pure alcohol).

* W is the individual’s body weight in pounds.

* r is the gender-specific alcohol distribution ratio (average of 0.73 for males and 0.66 for females to account for differences in body fat and water content).

* β is the metabolic elimination rate per hour, standardized at 0.015% per hour for most healthy adults.

* H is the total elapsed time in hours since the first drink was consumed.

Alcohol Metabolism and Safety Realities

How to Use This Calculator

Select your gender, enter the number of standard drinks consumed, your body weight in pounds, and the hours elapsed since your first drink.

Worked Example: 3 Drinks, 160 lb Male, 2 Hours Elapsed

3 standard drinks (1.8 oz pure alcohol), 160 lb male, 2 hours since the first drink.

Peak BAC: (1.8 × 5.14) / (160 × 0.73) ≈ 0.079%.

Current BAC after 2 hours of elimination: 0.079% - (0.015 × 2) ≈ 0.049% — below the 0.08% legal driving limit, but still in the "Impairment Detected" range above 0.05%.

Time to reach 0.00% BAC from the peak: 0.079 / 0.015 ≈ 5.3 hours.

Related Calculators

Related concepts

Widmark Formula

The clinical mathematical equation used to estimate BAC based on weight, sex, and alcohol consumption.

Standard Drink

A unit of alcohol measure containing 14 grams of pure ethanol.

Metabolic Elimination Rate

The rate at which the body processes and breaks down alcohol, typically 0.015% per hour.

Frequently Asked Questions

What is BAC?+

Blood Alcohol Concentration (BAC) is the metric used to measure the amount of alcohol in a person's bloodstream, expressed as a percentage.

What is the legal driving limit for BAC?+

In the United States and many other countries, the legal limit for driving is a BAC of 0.08%. In some regions, the limit is lower at 0.05% or zero.

How fast does the body metabolize alcohol?+

The body metabolizes alcohol at a constant rate of approximately 0.015% BAC reduction per hour. This rate cannot be sped up.

How much alcohol is in a standard drink?+

Why does BAC differ by gender?+

Men generally have higher water content and lower body fat percentages than women of equal weight, which dilutes alcohol more effectively and results in a lower BAC for the same intake.

Can drinking coffee or taking a cold shower lower my BAC?+

No. Coffee and cold showers may make you feel more awake, but they have zero effect on the rate at which your liver metabolizes alcohol.

How accurate is this BAC calculator?+

This calculator is a mathematical estimate based on average metabolic rates and the Widmark formula. Individual BAC values vary based on genetics, food intake, hydration, and medication.

Does food affect BAC?+

Drinking on an empty stomach causes alcohol to absorb more rapidly, leading to a higher and faster peak BAC. Food slows absorption but does not prevent alcohol from entering the bloodstream.

What is the Widmark formula?+

The Widmark formula is a clinical mathematical model used to estimate blood alcohol concentration based on body weight, biological sex, alcohol volume consumed, and time elapsed.

How long does it take to sober up completely?+

It depends on your peak BAC. Divide your peak BAC by the metabolic rate of 0.015% per hour to find the approximate number of hours required to reach 0.00%.

BAC Calculator

Inputs

Results

Widmark BAC formula

How the calculation works

Example BAC estimate

Learn more about this calculation

BAC Estimation Guide: Formula, Limits, and Safety

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

Sources & methodology

BAC Calculator

Inputs

Results

Key output metrics

Estimated BAC Decay Profile

How to understand and use this calculator

How Blood Alcohol Concentration (BAC) is Estimated

The Mathematics of the Widmark BAC Formula

Alcohol Metabolism and Safety Realities

How to Use This Calculator

Worked Example: 3 Drinks, 160 lb Male, 2 Hours Elapsed

Related Calculators

Related concepts

Frequently Asked Questions

Widmark BAC formula

How the calculation works

Example BAC estimate

Learn more about this calculation

BAC Estimation Guide: Formula, Limits, and Safety

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

Sources & methodology

Key output metrics

Estimated BAC Decay Profile

How to understand and use this calculator

How Blood Alcohol Concentration (BAC) is Estimated

The Mathematics of the Widmark BAC Formula

Alcohol Metabolism and Safety Realities

How to Use This Calculator

Worked Example: 3 Drinks, 160 lb Male, 2 Hours Elapsed

Related Calculators

Related concepts

Frequently Asked Questions