Bac Calculator
Calculate Blood Alcohol Content and estimate alcohol metabolism time. Free, fast, accurate — no signup, mobile-friendly,
Personal Information
Affects body water distribution ratio
Maximum is 24
Drinks Consumed
Important Disclaimer
- • This is an ESTIMATE ONLY - actual BAC varies widely by individual
- • Never use this to decide whether you are fit to drive
- • Do not rely on this for any legal or safety decision
- • When in doubt, do NOT drive or operate machinery - the only safe amount before driving is zero
- • Seek medical help if experiencing alcohol poisoning symptoms
Current BAC
Risk Level: Safe
Peak BAC
Maximum reached
Total Alcohol
Consumed
Time to Legal
Under 0.08% BAC
Time to Zero
Complete sobriety
Legal Status
Current Effects
- • Minimal to no effects
How it works
A blood alcohol content estimator uses the Widmark formula: it relates the alcohol consumed to your body weight and a sex-based distribution factor, then subtracts the alcohol your body has metabolized over time (roughly 0.015% BAC per hour).
Widmark BAC estimate
BAC ≈ (alcohol grams ÷ (body weight g × r)) × 100 − 0.015 × hours
- r
- distribution factor (~0.68 men, ~0.55 women)
- hours
- time since drinking began
Worked example
- Two standard drinks (~28 g alcohol)
- Person ~70 kg, r = 0.68, 1 hour elapsed
- Peak ≈ (28 ÷ 47,600) × 100 ≈ 0.059%
- Minus 0.015 × 1
Estimated BAC ≈ 0.044%.
Good to know
- This is a rough estimate only — actual BAC varies with food, metabolism, medication, and health. Never use it to decide whether to drive.
- In most US states the legal driving limit is 0.08%; it is lower for commercial and under-21 drivers.
- The only sure way to sober up is time; coffee, food, and water do not speed alcohol metabolism.
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Frequently Asked Questions
How is blood alcohol content (BAC) estimated?
This calculator uses the Widmark formula: the grams of alcohol consumed are divided by your body weight times a distribution factor (about 0.68 for men, 0.55 for women), then reduced by roughly 0.015% BAC for each hour since drinking began. It is a population-average estimate, not a measurement.
What BAC is the legal limit for driving?
In most US states the limit is 0.08% for drivers 21 and over; Utah uses 0.05%. Commercial drivers are typically limited to 0.04%, and drivers under 21 face zero-tolerance laws with limits of 0.00–0.02%. Impairment begins well below the legal limit.
How fast does the body eliminate alcohol?
The liver metabolizes alcohol at a fairly constant rate of about 0.015% BAC per hour — roughly one standard drink per hour. Coffee, cold showers, food, and exercise do not speed this up; only time lowers BAC.
What counts as a standard drink?
In the US, a standard drink contains about 14 grams of pure alcohol: a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, or a 1.5 oz shot of 80-proof spirits. Craft beers and large pours often contain substantially more than one standard drink.
Can I rely on this calculator to decide whether to drive?
No. Actual BAC varies with food intake, medications, hormones, fatigue, and individual metabolism, so any calculator can be off significantly. If you have been drinking, the only safe choice is not to drive.