Blood Alcohol Content (BAC) Calculator

How to calculate Blood Alcohol Content Calculator?

This calculator uses the Widmark formula to estimate blood alcohol concentration from the amount of alcohol consumed, body weight, gender constant, and time since drinking.

Key formula: BAC = (A * 5.14 / (W * r)) - 0.015 * H

Using the Blood Alcohol Content Calculator calculator: an example

Example values: 3 standard drinks (12 oz at 5% ABV), 170 lb male, 2 hours since first drink.

Step-by-step calculation:

1. Calculate pure alcohol: 3 drinks × 12 oz × 0.05 = 1.8 oz of pure alcohol.
2. Apply Widmark numerator: (1.8 * 5.14) / (170 * 0.73) ≈ 0.075 (pre-metabolism).
3. Subtract metabolism: 0.015 × 2 hours = 0.03. Final BAC ≈ 0.075 - 0.03 = 0.045.
4. Interpretation: ~0.045 BAC (0.045%), below many legal limits but can still cause impairment.

Frequently Asked Questions

Is this estimate legally binding?

No. This is an approximation and cannot replace breath or blood tests or legal determinations.

Why does gender affect the result?

The gender constant reflects average differences in body water distribution, which changes how alcohol disperses in the body and affects calculated BAC.

Can I lower my BAC quickly?

No. Alcohol is eliminated at an approximately fixed rate (about 0.015% BAC per hour); time is the only reliable way to reduce BAC.