Free Online Calculators
Estimate BAC by Widmark formula – not legally binding
The calculator estimates your blood alcohol concentration (BAC) in percent with the Widmark formula, from your weight, sex, standard drinks and the hours since your first drink. Four standard drinks put a 180 lb man at about 0.101%, and at about 0.071% two hours later. The US limit is 0.08% (Utah 0.05%). The result is an estimate only: if you have been drinking, do not drive.
4 standard drinks at a body weight of 180 lb give an estimated BAC of about 0.101% right after drinking. For women the value is roughly a quarter higher (distribution factor 0.55 instead of 0.68), and the body eliminates about 0.015% per hour. The chart shows BAC in percent for 1 to 8 drinks and 100 to 240 lb.
Each drink counts as one US standard drink with 14 g of pure alcohol.
| Drinks \ Body weight | 100 lb | 120 lb | 140 lb | 160 lb | 180 lb | 200 lb | 220 lb | 240 lb |
|---|---|---|---|---|---|---|---|---|
| 1 drink | 0.045 | 0.038 | 0.032 | 0.028 | 0.025 | 0.023 | 0.021 | 0.019 |
| 2 drinks | 0.091 | 0.076 | 0.065 | 0.057 | 0.050 | 0.045 | 0.041 | 0.038 |
| 3 drinks | 0.136 | 0.113 | 0.097 | 0.085 | 0.076 | 0.068 | 0.062 | 0.057 |
| 4 drinks | 0.182 | 0.151 | 0.130 | 0.113 | 0.101 | 0.091 | 0.083 | 0.076 |
| 5 drinks | 0.227 | 0.189 | 0.162 | 0.142 | 0.126 | 0.113 | 0.103 | 0.095 |
| 6 drinks | 0.272 | 0.227 | 0.195 | 0.170 | 0.151 | 0.136 | 0.124 | 0.113 |
| 8 drinks | 0.363 | 0.303 | 0.259 | 0.227 | 0.202 | 0.182 | 0.165 | 0.151 |
By the Widmark estimate, a 160-pound man reaches 0.24% with about 8 to 9 standard drinks in a short time, and a 130-pound woman with about 5 to 6. That is three times the 0.08% driving limit and a level with a real risk of alcohol poisoning.
You estimate it from the amount of pure alcohol you drank, your body weight and the share of body water, then subtract the alcohol your liver has broken down since your first drink. This is the Widmark approach, and it gives an estimate only — never a legally reliable value.
Yes, that is heavy drinking by any medical standard, since the liver breaks down alcohol far slower than that pace. Blood alcohol will keep climbing well above driving limits.
It can be, especially for a light person, on an empty stomach or where the legal limit is low. Zero-tolerance rules for novice and professional drivers make even one drink enough.
Plan on at least a couple of hours, because the body eliminates alcohol slowly and the peak comes some time after drinking. Waiting until you feel sober is not a reliable test.
By the Widmark estimate, about 3.5 standard drinks taken at once, or about 4 within one hour, because the body eliminates roughly 0.015% per hour. Food, drinking speed and metabolism shift the result, so never rely on the count to decide whether you can drive.
For men, heavy drinking generally means regularly exceeding the recommended daily and weekly limits, or frequent binge sessions with several drinks on one occasion. Health authorities define the thresholds in standard drinks per day and per week.
Yes, that amount is clearly measurable and will typically put you over common driving limits. Alcohol stays detectable for hours after the last sip.
Around five to six hours, because the liver eliminates alcohol at an average of about 0.015% BAC per hour. Coffee, food, cold showers or sleep do not speed this up.
The calculator estimates your blood alcohol concentration (BAC) with the Widmark formula. It adds up the pure alcohol in your drinks, divides it by your body weight multiplied by a distribution factor (0.68 for men, 0.55 for women) and subtracts the alcohol your body has already eliminated, about 0.015% BAC per hour. The result is shown in percent, the unit used for driving limits in the United States, Canada, the UK and Australia.
In the US, one standard drink contains about 14 grams (0.6 fl oz) of pure alcohol. That is roughly:
Craft beers, large pours and mixed drinks often contain more than one standard drink, so count them as one and a half or two.
A man who weighs 180 lb (81.6 kg) has four standard drinks, 56 grams of alcohol. Right after drinking, his estimated BAC is 56 ÷ (81,647 g × 0.68) × 100 ≈ 0.101%. Two hours later his body has eliminated about 0.030%, which leaves an estimated 0.071%. That is below 0.08% on paper, but judgment and reaction time are already impaired, and the real value can be higher.
You can be charged with impaired driving below these limits if alcohol affects your driving. The only safe BAC for driving is zero.
The liver breaks down alcohol at a fairly constant rate of about 0.015% BAC per hour. From 0.08% it takes around five to six hours to reach zero. Coffee, water, food or a cold shower do not speed this up. The calculator shows how many hours it takes until your estimated BAC is back to zero.
Never use the result to decide whether you are fit to drive. If you have been drinking, do not drive.
Many European countries state blood alcohol in per mille (‰). 0.5‰ equals 0.05% BAC and 0.8‰ equals 0.08%. Switch to metric units to enter your weight in kilograms; the result stays in percent.