BAC Calculator

Modify the values and click the Calculate button to use

BAC: 0.026%

Estimated BAC: 0.026%
Alcohol consumed: 26.0 g
Standard drinks: 1.9

BAC change with time

Estimated BAC

BAC is an estimate. It does not account for food, medications, liver health, or individual variation. Never drive after drinking; use a designated driver or ride service.

What this BAC calculator does

Blood alcohol concentration (BAC) is the percentage of alcohol in the blood. This calculator estimates BAC from body weight, time since the first drink, and the number and strength of standard drinks. It uses the Widmark formula, a common estimation method.

BAC is affected by many factors that a formula cannot capture, including food, medications, liver health, genetics, and drinking rate. The result is an estimate, not a legal or medical measurement.

How to use this calculator

Select sex.
Enter body weight and choose pounds or kilograms.
Enter the hours since the first drink.
Enter the number of beers, glasses of wine, and liquor shots.
Add an “other” drink size and ABV if needed.
Click Calculate.

The default example is a man weighing 155 lb who had two 12-ounce beers over two hours.

BAC formulas

Alcohol grams = volume × ABV × 0.789
BAC % = alcohol grams ÷ (weight kg × r) ÷ 10 − 0.015 × hours

r is about 0.66 for men and 0.55 for women. The 0.015 per hour term estimates alcohol elimination.

Standard drink approximations used here:

Beer: 330 ml at 5%
Wine: 150 ml at 12%
Liquor: 50 ml at 40%

What the results mean

The default example estimates about 0.026% BAC. The calculator also shows alcohol grams and standard drinks.

A BAC of 0.08% or higher is the legal driving limit in every U.S. state, but impairment can begin below that level. The only safe option after drinking is not to drive.

Assumptions and limitations

The Widmark formula is a rough estimate. It does not account for food, drinking speed, body composition, medications, liver disease, or individual elimination rates. It cannot tell you whether you are safe to drive.

Alcohol affects people differently, and tolerance does not reduce BAC. Never use this calculator to decide whether to drive or operate machinery.

Frequently asked questions

Can I use this to decide if I can drive?

No. Use a designated driver, public transportation, or a ride service. BAC estimates are not a safe driving test.

Why is my estimate different from a breathalyzer?

Breathalyzers measure alcohol in breath and use assumptions about blood-to-breath ratios. The Widmark formula uses average body-water distribution, so individual results vary.

Does coffee or a cold shower lower BAC?

No. Only time lowers BAC. Coffee, food, and cold showers may make someone feel more alert, but they do not reduce alcohol in the blood.

What is a standard drink?

In the U.S., a standard drink is about 14 g of pure alcohol: 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% liquor.

Reference tables

Standard drink examples

Type	Amount	Size	ABV
Beer	1	12 fl oz (355 mL)	5%
Wine	1	5 fl oz (148 mL)	12%
Distilled spirits	1	1.5 fl oz (44 mL)	40%
Malt liquor	1	12 fl oz (355 mL)	7%

BAC and impairment

BAC (%)	Behavior	Impairment
0.02–0.03	Mild relaxation	Slight loss of judgment
0.05	Lowered alertness	Reduced coordination and judgment
0.08	Impaired	Legal driving limit in all US states
0.15	Major impairment	Poor balance and slurred speech
0.30	Severe	Confusion, vomiting, risk of loss of consciousness

BAC estimates vary with food, medications, liver health, body composition, and drinking rate. Never drive after drinking.

Source

References:

Disclaimer

This calculator is for informational and educational purposes only. It is not a medical or legal measurement. Do not drive after drinking. Seek emergency help for signs of alcohol poisoning.

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