Blood Alcohol (BAC)
Estimate BAC (%) via Widmark formula. For reference only — never drive.
How it works
BAC ≈ alcohol_g ÷ (weight(kg) × 10 × r) − 0.015 × hours (male r=0.68, female r=0.55; 1 standard drink ≈ 14 g alcohol)
Estimated blood alcohol by the Widmark formula. This is a theoretical approximation affected by fasting, metabolism, medication, etc. Never drive after drinking.
Most regions set the legal driving limit at 0.02%–0.05% BAC.
FAQ
How much to reach the legal limit?
It varies by person; often 1–2 standard drinks approach the limit in many regions. The safest choice is not to drive after drinking.
Worked example
Male 70 kg, 3 standard drinks (~42 g alcohol), 2 hours later:
BAC ≈ 42 ÷ (70 × 0.68) − 0.015 × 2 ≈ 0.085% (about 85 mg/100 mL).
That exceeds the Chinese drunk-driving threshold of 80 mg/100 mL.
Notes and limitations
The Widmark equation has wide error: liver function, food, drinking speed and body composition all matter. Never use it to decide whether you can drive — the only safe limit is none.