About the BAC Calculator
BAC Calculator gives a rough estimate of blood alcohol content using the Widmark formula. Choose your sex and weight, add the drinks you had by type, number, size and strength, and enter the hours since your first drink. The tool works out the grams of pure alcohol, the peak BAC if everything is absorbed, the estimated BAC after the hours you entered and how long it takes to fall under 0.05 percent and to reach almost zero. Common presets such as beer, wine and spirits fill in size and strength, and you can enter your own. The result is only an estimate, because real blood alcohol depends on food, health, medicine and how fast you drink. Never use it to decide whether you can drive. Nothing you enter leaves your device.
Updated September 2026
How to use the BAC Calculator
- 1Choose male or female and enter your weight in kilograms or pounds.
- 2Pick a drink type, or choose custom and type its size in millilitres and its strength as a percentage.
- 3Enter how many of that drink you had. Use Add another drink for a different one.
- 4Enter the hours since your first drink, or leave 0 to see the peak.
- 5Read the estimate and the hours until it falls, and remember it is only a guide.
What BAC means
Blood alcohol content, or BAC, is the amount of alcohol in the blood, usually given as grams per 100 millilitres, which is the same as a percentage. A BAC of 0.05 percent means 0.05 grams of alcohol in each 100 millilitres of blood. It matters because balance, judgement, reaction time and vision get worse as it rises, and because it is how many countries set the drink-drive limit.
The figure from this tool is a model, not a measurement. It is useful for understanding how drinks add up and how slowly the body clears them, not for making safety decisions.
Working with the inputs
- Weight and sex set how much the alcohol is diluted in the body.
- Each drink's volume and strength give the grams of pure alcohol.
- The hours box turns the peak into an estimate for now.
- Choose Custom for cocktails, cans and unusual pours, and check the strength on the label.
Understanding the numbers
The peak BAC is the highest level if all the alcohol had been absorbed at once. In real life absorption takes 30 to 90 minutes, so the true peak is later and a little lower when you drink slowly. The tool then subtracts 0.015 percent per hour, a typical figure. People who drink often may clear a little faster, while some clear more slowly, and a large meal can change the curve.
The level names are rough bands. Even a low level can affect driving, and levels above 0.15 percent are dangerous. If someone is unconscious, vomiting repeatedly, cold or breathing slowly after drinking, call emergency services.
Safe use
Plan for a safe way home before you drink, and remember that the morning after can still be over the limit. Do not rely on an online estimate to decide whether to drive. For general health, BMI Calculator, Calorie Calculator and Water Intake Calculator help with related habits, and Unit Converter changes pounds to kilograms and millilitres to fluid ounces.
Features
- Widmark formula with a body-water factor for men and women
- Drink presets plus custom size and strength
- Up to six different drinks together
- Peak BAC and BAC after a chosen number of hours
- Hours until under 0.05 percent and until near zero
- Plain-language level with safety warnings
- Kilograms or pounds
- Runs in your browser, nothing stored
Frequently asked questions
How is BAC estimated?
The Widmark formula divides the grams of alcohol you drank by your body weight times a body-water factor, 0.68 for men and 0.55 for women, then subtracts about 0.015 percent for each hour that has passed. It gives a rough average that real people can differ from a lot.
How many grams of alcohol are in a drink?
Multiply the volume in millilitres by the strength as a decimal and by 0.789, the density of alcohol. A 330 ml beer at 5 percent has 330 × 0.05 × 0.789, about 13 grams. A 150 ml glass of 12 percent wine has about 14 grams, and a 40 ml spirit at 40 percent has about 12.6 grams.
How long does it take to sober up?
On average the body clears about 0.015 percent BAC per hour, so a BAC of 0.06 percent takes about four hours to fall to zero. Coffee, cold showers and food do not speed it up, and some people clear more slowly. The tool shows the hours to near zero and to below 0.05.
Can I use this to check if I can drive?
No. It is only a rough estimate and it can be wrong by a wide margin. Two people of the same weight can have different BAC after the same drinks, and alcohol affects driving skill even below legal limits. If you have been drinking, do not drive.
Why do men and women get different results?
On average women have less body water and more body fat than men of the same weight, so the same amount of alcohol reaches a higher concentration. The formula uses a lower factor for women to reflect that average. Individuals vary widely.
What affects real blood alcohol content?
Food in the stomach slows absorption, and drinking fast pushes the peak higher. Medicines, illness, tiredness, body fat, age and how often you drink also matter. Some people have a genetic difference in how they process alcohol. The formula ignores all of these.
What are the legal driving limits?
They differ by country and sometimes by driver type. Many countries use 0.05 percent, the United States uses 0.08 percent in most states, some places allow 0.02 to 0.03 percent, and some allow none at all for new or professional drivers. Check the law where you are.