Blood alcohol

A calculator that models absorption and elimination properly, instead of dividing by a constant.

Read in
Legal limit
0.00 g/L
Barely there

Subtle warmth and a small mood lift. Most people notice nothing, though fine-motor tests already show a change.

Under the 0.50 g/L limit.

0.000.200.400.6014:1516:1518:1520:15Croatia — general0.29g/Lnow
Drag across the chart to read any moment.
Peak 0.35 g/L at 15:35 · relaxed
Under the limit Never over it Croatia — general
Completely sober 6 h 16 min
Consumed 35 g 3.5 × EU / WHO unit
Still in the stomach 0.0 g everything is absorbed
Energy 245 kcal from the alcohol alone

You

Body composition sets how much water the alcohol dissolves into, which is the single biggest factor.

Biological sex
kg
cm
years

Body water falls with age, which the Watson model accounts for.

Distribution model

Mean of Watson, Forrest and Seidl — the usual eBAC approach.

Stomach and metabolism

Food does not stop you getting drunk, but it slows absorption enough to blunt the peak.

Last meal
1 h

A meal keeps working for a few hours, then the stomach is empty again.

How often you drink
Liver function

What you drank

Every drink carries its own size, strength, timing and pace.

1 h ago

Everything else is timed from there. Clock time 14:15.

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Model and units

Absorption
Elimination
Standard drink
:1

Only affects the breath units. 2100 is the US convention, 2300 the UK one.

Under the hood

The numbers this run is actually using.

Widmark factor r
0.735 L/kg
Volume of distribution
57.3 L
Total body water
45.8 L (59% of mass)
Elimination rate beta
0.165 g/L/h (0.0165 %/h)
Michaelis-Menten Vmax / Km
0.179 / 0.082 g/L
Mean absorption constant
3.55 /h
Stomach fullness at first drink
68%
Reaching the bloodstream
29.9 of 34.5 g (87% bioavailable)

Every model, side by side

  • Consensus average 0.735
  • Watson (1980) 0.720
  • Forrest (1986) 0.719
  • Seidl (2000) 0.765
  • Body composition 0.724
  • Widmark average 0.730
  • Widmark conservative 0.680

Blood is taken to be 80% water, so r converts total body water into a blood-equivalent distribution volume.

This is an estimate, not a breathalyser. Real blood alcohol varies by roughly ±20% between people with identical inputs, and considerably more if you have been vomiting, are on medication, or have eaten something unusual. Never use a calculator to decide whether you can drive. If you have had anything at all to drink, do not drive.

Where the numbers come from
  • Widmark, E.M.P. (1932) — the original distribution model, and the r = 0.68 / 0.55 conservative forensic pair still used in court.
  • Watson, P.E., Watson, I.D. & Batt, R.D. (1980), Am J Clin Nutr — total body water from age, height and mass.
  • Forrest, A.R.W. (1986), J Forensic Sci Soc — r estimated from body mass index.
  • Seidl, S., Jensen, U. & Alt, A. (2000), Int J Legal Med — r regressed on mass and height in 273 men and 256 women.
  • Gullberg, R.G. — the uncertainty coefficients behind the Monte-Carlo band (r 9.2%, beta 22%, strength 3%, volume 2%, correlation between r and beta −0.135).
  • Holford, N.H.G. (1987), Clin Pharmacokinet — capacity-limited ethanol elimination, giving the Michaelis constant near 0.08 g/L.
  • Frezza, M. et al. (1990), NEJM — first-pass gastric metabolism, and why it differs by sex and with H2 blockers.

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