BAC Calculator
Estimate blood alcohol content (BAC) from your weight, sex, drinks and time. Educational estimate using the Widmark formula. Never use it to decide if you can drive.
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About the BAC Calculator
This BAC calculator estimates blood alcohol concentration with the Widmark formula. It uses your body weight, sex (which affects the body-water distribution ratio), the number of standard drinks (about 14 g of pure alcohol each) and the hours since you started drinking, assuming the body eliminates roughly 0.015 % BAC per hour.
Important: real BAC varies with food, medication, genetics, drink strength and health. This tool is for education only and is not a safe way to decide whether you can drive. The only safe amount of alcohol before driving is none. Arrange a ride.
How to use it
- Select your sex and enter your weight in pounds.
- Enter the number of standard drinks and the hours since your first drink.
- Press Estimate BAC to see the estimate and the time to sober up.
What counts as one standard drink?
| Drink | US standard serving |
|---|---|
| Regular beer (5 %) | 12 fl oz |
| Wine (12 %) | 5 fl oz |
| Distilled spirits (40 %) | 1.5 fl oz shot |
Craft beers, large pours and mixed drinks often contain 1.5 to 3 standard drinks, so count carefully.
BAC levels and effects
| BAC | Typical effects |
|---|---|
| 0.02 – 0.03 % | Slight mood change, mild relaxation |
| 0.05 % | Reduced coordination and reaction time |
| 0.08 % | Legal driving limit in most US states (0.05 % in Utah) |
| 0.15 % | Major loss of balance and judgment |
| 0.30 %+ | Risk of loss of consciousness and death |
Widmark formula
BAC (%) = [alcohol in grams ÷ (body weight in grams × r)] × 100 − 0.015 × hours. r is about 0.68 for men and 0.55 for women.
Frequently asked questions
How is BAC calculated?
With the Widmark formula: grams of alcohol divided by body weight times a body-water constant (0.68 men, 0.55 women), minus about 0.015 % per hour of elimination.
How long does it take to sober up?
On average the body clears about 0.015 % BAC per hour. Coffee, cold showers or water do not speed it up.
What is the legal BAC limit for driving in the US?
0.08 % in 49 states for drivers 21 and over, and 0.05 % in Utah. Commercial drivers and under-21 drivers face lower limits.
Is this BAC calculator accurate?
It is an estimate. Food, medication, drink strength and individual metabolism change real BAC, so do not rely on it for driving decisions.
Why do women have a higher BAC than men for the same drinks?
On average women have less body water and a different alcohol metabolism, so the same amount of alcohol gives a higher concentration.
Last reviewed: November 2026. Educational estimate only, not a safe-driving tool.
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