BAC Calculator
Estimate your blood alcohol content (BAC) based on number of drinks, time elapsed, body weight and sex. For informational purposes only — never drink and drive.
How to use the BAC Calculator
- Enter your inputs into the BAC Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The Widmark BAC formula
BAC = (A × 5.14 / (W × r)) − (0.015 × t)
A is total alcohol in grams (drinks × 14g per standard drink). W is body weight in pounds. r is the distribution ratio (0.73 men, 0.66 women). t is hours since first drink. Result is %.
Worked example
A 180 lb man having 4 standard drinks over 2 hours: A = 4 × 14 = 56 g. BAC = (56 × 5.14 / (180 × 0.73)) − (0.015 × 2) = 2.19 − 0.03 = 0.19% — well above the 0.08% legal limit.
Frequently asked questions
What is the legal driving limit?
In the US: 0.08% BAC for adults (0.05% in Utah). In most of Europe: 0.05%. For commercial drivers (US): 0.04%. Under 21 zero-tolerance laws apply in all US states.
How quickly does BAC decrease?
About 0.015%–0.020% per hour. There is no way to speed up alcohol metabolism — coffee, food and cold showers don't help. The only treatment for being drunk is time.
How accurate is this estimate?
Within ±0.02% for typical adults, but many factors affect actual BAC: meal contents, hydration, medications, individual liver function, drink mixers. Never rely on calculations to decide whether to drive.