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.

Bac Calculator

Calculate Blood Alcohol Content and estimate alcohol metabolism time. Free, fast, accurate — no signup, mobile-friendly,

Personal Information

Gender

Affects body water distribution ratio

Weight

Weight Unit

Time Since Drinking Started

Maximum is 24

Time Unit

Drinks Consumed

Drink 1

Type

Amount

Unit

Alcohol %

Important Disclaimer

• This is an estimate only - actual BAC varies by individual
• Do not rely on this for legal or safety decisions
• When in doubt, do not drive or operate machinery
• Seek medical help if experiencing alcohol poisoning symptoms

Current BAC

0.000%

Risk Level: Safe

Peak BAC

0.025%

Maximum reached

Total Alcohol

14.0g

Consumed

Time to Legal

Legal now

Under 0.08% BAC

Time to Zero

Zero now

Complete sobriety

Legal Status

Driving Legal:Yes

Work Safety:Safe

Public Intox Risk:Low

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.