How to Calculate BAC & Alcohol Recovery
What is BAC & Alcohol Recovery?
Blood Alcohol Concentration (BAC) estimates how much alcohol is in the bloodstream, calculated using the Widmark formula. BAC is influenced by units consumed, body weight, time elapsed, and biological sex (different body water percentages).
Step-by-Step Guide
- 1Widmark formula: BAC% = (Alcohol grams) / (Body weight kg × 1000 × r) − 0.015 × hours
- 2r = 0.68 (males), 0.55 (females) — distribution factor
- 31 UK unit = 10ml pure alcohol = ~8g
- 4Alcohol eliminated at ~0.015% per hour (linear, not exponential)
Worked Examples
Input
4 pints (4% lager) · 70kg male · 2 hours drinking
Result
BAC ≈ 0.087% (over UK legal limit of 0.08%)
Drive limit 0.05% in Scotland, 0.08% in England/Wales
Ready to calculate? Try the free BAC & Alcohol Recovery Calculator
Try it yourself →