BAC Calculator
⚠️ Educational estimate only — not for deciding whether it's safe to drive or to determine legal compliance. See the note below.
Enter valid weight, drinks, and hours (all non-negative).
This uses the Widmark formula, a widely-cited estimate — it does not account for food intake, medication, liver function, body fat percentage, or many other individual factors that meaningfully change real BAC. The US legal driving limit is 0.08% in most states, but impairment begins well below that. If you've been drinking, the only safe choice is not to drive — use a rideshare, taxi, or a sober driver, regardless of what any calculator shows.
Free BAC calculator using the Widmark formula — a clearly-labeled educational estimate, not a tool for deciding whether it's safe to drive. If you've been drinking, the only safe choice is not to drive, regardless of what any calculator shows.
How it works
- Enter your sex, weight, standard drinks consumed, and hours since your first drink
- See your estimated blood alcohol content
Frequently asked questions
What is a 'standard drink'?
In the US, one standard drink contains about 14 grams of pure alcohol — roughly a 12oz beer (5% ABV), a 5oz glass of wine (12% ABV), or 1.5oz of distilled spirits (40% ABV).
Can I use this to decide if I'm okay to drive?
No. This is an educational estimate that doesn't account for food intake, medication, liver function, body fat percentage, or many other factors that meaningfully change real BAC. If you've been drinking, don't drive — use a rideshare, taxi, or sober driver instead, regardless of any calculator result.
Related tools
From the blog
Update history
- 2026-09-03 The result now changes color and size based on how close it is to the 0.08% legal limit, so the comparison is visible at a glance.
- 2026-09-03 Weight is now a slider instead of a number field, and the sex toggle shows an icon for each option.
- 2026-09-01 Added: a cover image — used as the card thumbnail, social share image, and blog title image.
- 2026-09-01 Launched: BAC estimator using the Widmark formula, with explicit safety framing that this is not a tool for driving decisions. Entirely client-side.