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%.

health calculator

BAC Calculator

Estimate blood alcohol concentration based on drinks, weight, and time.

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

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.

Related guides

Learn more about this calculation

Guide

BAC Estimation Guide: Formula, Limits, and Safety

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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.

health calculator

BAC Calculator

Estimate blood alcohol concentration based on drinks, weight, and time.

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

Summary

Key output metrics

Current BAC

0.049%

Some Alcohol Effects (> 0%)

Peak BAC

0.079%

Maximum value reached.

Hours to Sobriety

3.3 hrs

Time until 0.00% BAC.

D3 visualization

Estimated BAC Decay Profile

Linearly models the standard metabolization of ethanol (average decay of 0.015% per hour) over elapsed time.

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.

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.