BAC Calculator

Use this Blood Alcohol Concentration (BAC) calculator to estimate your current blood alcohol level, peak BAC, impairment category, and time until sober using Widmark's formula.

How to use this calculator

1. Select your gender and unit system.
2. Enter the number of standard drinks consumed (1 drink = 12 oz beer, 5 oz wine, 1.5 oz 80-proof spirit).
3. Enter hours elapsed since starting drinking.
4. View estimated current BAC %, peak BAC, legal driving status (0.08% limit), and time until sober.

Formula & method

Widmark BAC & Metabolism Formula

BAC = [(Drinks × 14g) ÷ (Weight(g) × r)] × 100 − (0.015 × Hours)

r = 0.68 (males), 0.55 (females). Weight in grams = Weight(kg) × 1000.

Example

Male 75 kg, 3 drinks over 2 hours → Peak BAC ≈ 0.082%, Current BAC ≈ 0.052%.

Key insights

• One standard US drink contains approximately 14 grams of pure ethanol.
• The body metabolizes alcohol at a roughly constant average rate of 0.015% BAC per hour.
• Coffee, cold showers, or exercise do not speed up alcohol metabolism — only time reduces BAC.

How to interpret your result

Estimated BAC

Calculated percentage of alcohol present in blood stream.

Sober Time

Estimated hours required for BAC to decay to 0.00%.

Frequently asked questions

What is the legal BAC limit for driving?

In the United States and Canada, the legal limit for adult non-commercial drivers is 0.08% BAC.

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