Blood Alcohol Calculator
Estimate your BAC with the Widmark formula.
How to use
- 1 Enter the number of standard drinks you have consumed.
- 2 Enter your body weight and pick kilograms or pounds.
- 3 Select your biological sex and the hours since your first drink.
- 4 Read the estimated BAC and time-to-sober figure.
About Blood Alcohol Calculator
The Blood Alcohol Calculator estimates your Blood Alcohol Concentration (BAC) using the well-known Widmark formula.
Enter how many standard drinks you have had, your body weight, your biological sex and how long ago you started drinking, and it returns an estimated BAC as a percentage along with a plain-language reading and a rough time until your BAC returns to zero.
The maths works like this: the alcohol you drink is distributed through the water in your body, which is captured by a sex-specific ratio in the Widmark equation.
Heavier people and those with a higher body-water ratio reach a lower peak BAC for the same amount of alcohol.
Your liver then clears alcohol at roughly 0.015 percentage points per hour, so the calculator subtracts that for every hour since your first drink and never lets the result fall below zero.
This is strictly an educational estimate.
Real BAC depends on many factors the formula cannot see — food, hydration, medication, drinking pace, individual metabolism and the exact strength of each drink.
Because of that, you should never use this tool to decide whether it is safe to drive or operate machinery.
The safest BAC for driving is always zero.
Everything is calculated locally in your browser; nothing you enter is uploaded, logged or stored, and it works offline once loaded.
FAQ
Can I rely on this to decide if I can drive?
No. This is an educational estimate only and cannot account for everything that affects your real BAC. Never use it to judge fitness to drive — the only safe level for driving is zero.
What counts as a standard drink?
By default the tool assumes 14 grams of pure alcohol per drink, the US standard. That is roughly a 12 oz beer, a 5 oz glass of wine, or a 1.5 oz shot of spirits. Drink sizes and strengths vary, so adjust your drink count accordingly.
Why does sex change the result?
The Widmark formula uses a body-water distribution ratio that differs by sex, which affects how concentrated a given amount of alcohol becomes. It is a population average, not a statement about any individual.