About the BAC Calculator

Blood Alcohol Content (BAC) is the percentage of alcohol in your bloodstream, used as a rough indicator of alcohol impairment.

Formula Used

BAC% = (Alcohol grams / (Weight(g) × r)) × 100 - (Hours × 0.015) (r = 0.68 for men, 0.55 for women; 1 standard drink ≈ 14g alcohol)

How It Works

This calculator uses the Widmark formula, factoring in standard drinks consumed (each assumed to contain about 14g of pure alcohol), your body weight, gender, and time elapsed since drinking.

Step by Step

Estimate total grams of alcohol consumed (drinks × 14g).
Divide by your body weight in grams multiplied by your gender's distribution ratio.
Subtract the amount metabolised over time (about 0.015% per hour).

Worked Example

Example: A 70 kg man having 2 drinks over 1 hour:

BAC = (28 / (70000×0.68)) × 100 - (1×0.015) ≈ 0.044%

This is an estimate only — never use it to decide whether to drive.

Frequently Asked Questions

Is this calculator accurate enough to drive?

No. This is only a rough estimate for educational purposes and should never be used to decide whether it's safe to drive - many factors affect actual BAC.

What counts as one standard drink?

This calculator assumes about 14 grams of pure alcohol per standard drink, roughly equivalent to a small beer or a standard peg of spirits.

Why does gender affect BAC?

Women generally have a lower body water percentage than men, which the Widmark formula accounts for using different distribution ratios.

CALCULATOR EXPERT

BAC Calculator