Alcohol Blood Concentration Calculator

Drink accounting alone needs no body weight; a BAC estimate does.
How many drinks of the size and strength below.
Typical beer 4-6%, wine 12-14%, spirits 40%.
Metric uses kilograms and centimetres; US uses pounds with feet and inches; UK uses stones and pounds.
Body weight: kilograms (metric), pounds (US) or whole stones (UK). Needed only for a BAC estimate.
Only used with UK stones-and-pounds: the pounds part, e.g. 11 st 4 lb is weight 11 and extra pounds 4.
The Widmark ratio r approximates the fraction of body mass that is water, which is where alcohol distributes.
Only used when sex is set to "custom". Reported ranges are roughly 0.60-0.75 for men and 0.50-0.66 for women.
Alcohol leaves the blood at a roughly constant rate. 0.015 %/hour is the standard forensic average; reported values run 0.012-0.020.
US states other than Utah use 0.08%; Utah uses 0.05%. England, Wales and Northern Ireland use 0.08%, Scotland 0.05%.
Estimated BAC now
0.0425 % (g/100 mL)
Blood Alcohol (BAC) Calculator
Pure alcohol consumed
39.4500 g
Pure alcohol consumed
50.000 mL
US standard drinks (14 g each)
2.8179
UK alcohol units (10 mL each)
5.0000
BAC if all of it were absorbed and none eliminated
0.0725 %
BAC in per mille
0.425 g/L
Hours until below the legal limit
0.00 hours
Hours until no alcohol remains
2.83 hours
Over the legal limit
no
Typical effects at this BAC
0.02% - some loss of judgement, relaxation, slight body warmth
Widmark ratio used
0.680
Body weight used
80.00 kg
Worked out from NHTSA, Office of Program Development and Evaluation - Computing a BAC Estimate (the Widmark form BAC = A x 5.14 / (W x r) - 0.015 H, with r = 0.68 men and 0.55 women) and 4 other sources.
Widmark assumes every drink is already fully absorbed. Within the first hour or two of drinking the real BAC is usually still rising, so a low estimate here does not mean a low BAC later.
This is a population-average estimate, not a measurement. Real BAC varies widely with absorption, food, sex, medication, liver function and tolerance, and can still be rising after the last drink. Never use it to decide whether it is safe or legal to drive. The only safe amount of alcohol before driving is none.

How this is worked out

11 steps
  1. Total liquid = 2 x 500 ml = 1000 mL
  2. Pure ethanol = 1000 mL x 5% = 50 mL
  3. Mass of ethanol = 50 mL x 0.789 g/mL = 39.45 g
  4. US standard drinks = 39.45 g / 14 g = 2.818
  5. UK units = 50 mL / 10 mL = 5
  6. Widmark ratio r = 0.68 (male)
  7. Body weight = 80 kg
  8. BAC before elimination = 39.45 g / (10 x 0.68 x 80) = 0.07252%
  9. Alcohol eliminated in 2 h = 0.015 x 2 = 0.03%
  10. BAC now = 0.07252 - 0.03 = 0.04252%
  11. Time until BAC reaches zero = 0.04252 / 0.015 = 2.83 h

Results are general information, not financial, tax, legal, medical or engineering advice.