A Blood Alcohol (BAC) Calculator computes blood alcohol (bac) from the inputs you provide. It applies the standard formula to the values you enter and returns the result instantly, without sending any data to a server. Estimate BAC based on drinks consumed, body weight, gender, and time elapsed.
Rough blood alcohol estimate. Not for legal use.
Widmark: BAC = (alcohol_g / (weight_g x r)) x 100 - 0.015 x hours, where r is 0.68 (M) or 0.55 (F). Estimate only.
Estimate blood alcohol content based on drinks, weight, gender, and time.
The BAC Calculator estimates your blood alcohol content using the Widmark formula. It considers body weight, gender (body water ratio differs), number of standard drinks, and time elapsed. It also shows when your BAC will return to zero.
Important: India has one of the strictest legal limits - 0.03% BAC (30 mg/100mL). Even 1-2 drinks can put you over the limit. This calculator is for educational purposes only.
The BAC calculator on this page uses the Widmark equation, published by Swedish chemist Erik Widmark in 1932 and still the basis of forensic and clinical alcohol estimation almost a century later. Widmark observed that ethanol distributes across the body's total water volume, not its total mass, so peak blood concentration depends on body weight, the body-water fraction (constant r), and grams of pure alcohol consumed. The formula does not need a breathalyser, a blood draw, or a saliva strip: only weight, sex, drinks, and elapsed time.
Pure ethanol is the only thing that matters. A 12 oz US beer at 5 percent ABV, a 5 oz pour of wine at 12 percent ABV, and a 1.5 oz spirit shot at 40 percent ABV each contain about 14 g of pure alcohol and count as one US standard drink. UK units are smaller (8 g), Australia uses 10 g, and Japan, France, and Germany sit between 10 and 14 g. If you are tracking pints of strong craft beer (often 7 to 9 percent ABV) or generous restaurant wine pours (6 to 8 oz), one glass can equal 1.5 to 2 standard drinks.
BAC percent = (alcohol_g / (weight_g x r)) x 100 - 0.015 x hours alcohol_g = drinks x 14 g (US standard) weight_g = body weight in grams (kg x 1000, or lb x 453.592) r = 0.68 for men, 0.55 for women 0.015 = elimination rate per hour (median adult) hours = time since the first drink
A 75 kg man drinks three 12 oz beers at 5 percent ABV over two hours. Step through the math the calculator runs:
Driving thresholds vary by more than 4x across major economies. The table below shows current limits for licensed adult drivers; novice and commercial drivers usually face stricter caps.
| Country | Adult limit (BAC percent) | Notes |
|---|---|---|
| India | 0.03 | Motor Vehicles Act 1988, Section 185 |
| Japan | 0.03 | Strict enforcement, criminal record on first offence |
| Sweden | 0.02 | Among the lowest in Europe |
| Germany, France, Italy | 0.05 | Most EU member states |
| Scotland | 0.05 | Lower than rest of UK since 2014 |
| England, Wales, NI | 0.08 | Among the highest in Europe |
| United States, Canada | 0.08 | Utah lowered to 0.05 in 2018 |
| Australia | 0.05 | Uniform across all states |
| UAE, Saudi Arabia | 0.00 | Zero tolerance |
India sets the legal driving BAC at 0.03 percent (30 mg per 100 mL of blood), one of the strictest in the world. The United States and England, Wales and Northern Ireland use 0.08 percent. Scotland, most of Europe, and Australia use 0.05 percent. Japan uses 0.03 percent and Sweden 0.02 percent. Commercial drivers and novice drivers usually face a lower cap (often 0.02 percent or zero tolerance).
The liver metabolises alcohol at roughly 0.015 percent BAC per hour, equivalent to about one standard drink per hour for most adults. A 0.08 percent BAC therefore needs about 5 to 6 hours to fall to zero, and a 0.12 percent BAC needs about 8 hours. Coffee, cold showers, exercise, food eaten after drinking, and energy drinks do not speed up metabolism; they only make you feel more alert at the same BAC.
Widmark uses a body-water distribution constant r of about 0.68 for men and 0.55 for women. Women have a higher proportion of body fat, which holds less water, so the same dose of alcohol distributes into a smaller water volume and produces a higher peak BAC. Lower gastric alcohol dehydrogenase activity in women also contributes. A 60 kg woman and a 60 kg man drinking three standard drinks will not reach the same BAC.
A US standard drink contains 14 g of pure alcohol, the UK unit is 8 g, and Australia uses 10 g. Examples of 14 g: a 12 oz beer at 5 percent ABV, a 5 oz wine at 12 percent ABV, or a 1.5 oz spirit at 40 percent ABV. Many craft beers, large wine pours, and double measures contain 1.5 to 2 standard drinks, which the calculator will not catch unless you adjust the count.
No. The Widmark formula gives a rough population-average estimate. It ignores stomach contents, recent meals, body composition variation, medications, individual liver enzyme activity, and absorption rate. Real BAC measured by a breathalyser or blood draw can differ by 0.02 to 0.04 percent from the calculator output. Treat this tool as educational. Never drive based on a Widmark estimate that sits close to the legal limit.