BAC (Blood Alcohol Concentration) Calculator

Sex

Widmark r: 0.73 (M), 0.66 (F)

Body Weight

Standard Drinks

1 standard drink ≈ 14 g ethanol (≈ 12 oz beer 5%, 5 oz wine 12%, 1.5 oz 40% spirits).

Hours Since Drinking Started

Metabolism assumed at 0.015 BAC/hour (β).

Advanced (itemized drinks) — use if you know ounces and ABV

Beer Volume (oz)

Typical beer: 4%–7% ABV

Beer ABV (%)

Wine Volume (oz)

Typical wine: 9%–15% ABV

Wine ABV (%)

Spirits Volume (oz)

Typical spirits: 35%–50% ABV

Spirits ABV (%)

If Advanced is provided and valid, it overrides Standard Drinks.

BAC Calculator – Quick Cheat Sheet

Widmark Formula: BAC ≈ (A / (W × r)) × 100 − β × t
A = grams of ethanol (1 std drink ≈ 14 g).
W = body weight in grams (lb × 453.592, kg × 1000).
r = body water constant (0.73 male, 0.66 female).
β = elimination per hour (assumed 0.015 BAC/h).
t = hours since drinking started.
Standard drink examples: 12 oz beer @5%, 5 oz wine @12%, 1.5 oz spirits @40%.
Advanced inputs convert ounces & ABV → grams using ethanol density 0.789 g/mL.

Edge cases & notes

β varies by person (~0.010–0.020). Real BAC can be higher or lower than estimated.
Food, health, and timing affect absorption; this tool assumes a simplified model.
If Advanced itemization is valid, it overrides Standard Drinks.
Outputs are rounded; use the details section for intermediate values.