BACWatch

BAC Calculator

Rough Widmark BAC estimate — never rely on it to decide whether to drive.

Weight (kg)

Standard drinks

Hours since first drink

Estimated BAC

52.35 ‰

Below the 0.08% legal driving limit — do not drive if you feel impaired

Widmark formula — this is a rough estimate. Never rely on it to decide whether to drive.

What you entered

Gender: MaleWeight: 75 kgStandard drinks: 3Hours since first drink: 2

1
Total alcohol consumed
3 drinks × 14 g= 42.0 g
2
Widmark formula (before elimination)
42.0 ÷ (75 kg × 1000 × 0.68 r) × 100= 0.082%
3
Alcohol eliminated over time
0.015%/hr × 2 hours= 0.030%
4
Estimated current BAC
0.082% − 0.030%= 0.052%

Result

Estimated BAC: 0.052%

This estimate is below the 0.08% legal driving limit, but individual tolerance varies — never drive if you feel impaired regardless of what a calculator says.

Estimated blood alcohol content by drinks, weight, and time

The Widmark estimate divides alcohol consumed by body water, then subtracts roughly 0.015 percentage points per hour for metabolism. The legal driving limit is 0.08% across most of the US and 0.05% in much of Europe.

Drinks	Sex	Weight	Hours since first drink	Estimated BAC
1	Male	80 kg	1	0.011%
2	Male	80 kg	1	0.036%
3	Male	80 kg	2	0.047%
4	Male	80 kg	2	0.073%
5	Male	90 kg	3	0.069%
2	Female	60 kg	1	0.070%
3	Female	60 kg	2	0.097%
4	Female	70 kg	2	0.115%

This is an estimate, not a breathalyser. Food, medication, hydration, liver function, and individual metabolism all move the real figure, and the error can run in either direction. Never use a calculator to decide whether you are safe to drive.

How the Widmark formula works

It estimates BAC from the amount of alcohol consumed, body weight, sex (which affects body water percentage), and time elapsed since drinking began — the body metabolizes alcohol at a roughly constant rate over time, which the formula subtracts out.

Why this is an estimate, never a decision tool

Individual metabolism, food intake, medication, and hydration all shift real BAC away from this formula's prediction — never use an estimate like this to decide whether it's safe to drive; only a certified breathalyzer or blood test is reliable for that.

Frequently asked questions

What BAC is legally drunk?

In most US states, 0.08% BAC is the legal limit for driving. Commercial drivers: 0.04%. Under 21: zero tolerance (0.00–0.02% depending on state). Many countries use lower limits: 0.05% (Australia, most of Europe) or 0.03% (India, Japan). Impairment begins well below the legal limit — reaction time measurably slows at 0.02%.

How long does it take to sober up?

The body metabolizes alcohol at roughly 0.015% BAC per hour — about one standard drink per hour. At 0.08% BAC, it takes approximately 5.3 hours to reach 0.00%. At 0.15% (heavily intoxicated), about 10 hours. Nothing speeds this up — coffee, cold showers, and food do not accelerate alcohol metabolism.

Why do women reach higher BAC than men?

Women have a lower percentage of body water than men (52% vs 61%), so alcohol is more concentrated. Women also produce less alcohol dehydrogenase (the enzyme that breaks down alcohol). A 60 kg woman drinking the same amount as a 60 kg man will have a higher BAC — the Widmark formula accounts for this with sex-specific body water constants.