BAC Calculator

Enter the number of standard drinks, your body weight, how many hours have passed and your sex. The calculator returns an estimated blood alcohol content and how long until it reaches zero.

• Standard drink — about 0.6 fl oz (14 g) of pure alcohol: a 12 oz beer, 5 oz wine or 1.5 oz spirits.
• Hours — time since your first drink; the body clears alcohol continuously.
• Weight and sex — both affect how concentrated alcohol becomes in your blood.
• Estimate only — real BAC depends on food, medication, genetics and drinking speed.

A 180 lb male who has 3 standard drinks over 2 hours:

• BAC ≈ (3 × 0.6 × 5.14) ÷ (180 × 0.73) − 0.015 × 2
• BAC ≈ 0.070 − 0.030 = 0.040%
• At this level, driving is impaired and may be illegal in many places.

Never use this estimate to decide whether it is safe to drive. Time is the only thing that lowers BAC.

• Under 0.02% — typically little noticeable impairment, but any alcohol affects reaction time.
• 0.05–0.08% — reduced coordination and judgment; over the limit in many countries.
• 0.08% and above — legally intoxicated in the US and unsafe to drive.

• NIAAA — What is a standard drink?
• CDC — Alcohol and public health