SmaartCoachBAC Calculator
Roughly estimate blood alcohol content from drinks and time.
Your details
One standard drink = 14 g of alcohol (a 12 oz beer, 5 oz wine, or 1.5 oz spirit).
This is a rough Widmark estimate and can be very wrong for any individual. Never use it to decide whether to drive. If you have been drinking, do not drive.
This tool is for general education only and is not medical advice. Talk to a healthcare professional about your results.
Blood alcohol content (BAC) is the percentage of alcohol in your bloodstream. This tool gives a rough estimate using the Widmark formula, based on how much you drank, your body weight and sex, and how long ago you started.
How BAC is estimated
The calculation starts from the amount of pure alcohol you consumed, measured in standard drinks. One standard drink contains about 14 grams of pure alcohol, roughly a 12 ounce beer, a 5 ounce glass of wine, or a 1.5 ounce shot of spirits. The formula then accounts for your body size and sex, and subtracts the alcohol your body clears over time.
Why it is only an estimate
Real blood alcohol depends on many things this formula cannot capture: whether you have eaten, your metabolism, medications, liver health, and how quickly you drank. Two people who drink the same amount can end up with very different actual levels, so treat the result as a rough guide only.
Never use this estimate to decide whether it is safe to drive. Impairment begins well before any legal limit, and only time lowers your BAC. Coffee, water, food, and a cold shower do not speed it up. If you have been drinking, do not drive.
Alcohol and your goals
Beyond safety, alcohol is calorie dense and can stall fat loss, disrupt sleep, and slow recovery. If your health and fitness goals matter to you, SmaartCoach helps you plan around the occasions that do not, so a night out does not undo a good week.
Frequently asked questions
How is BAC calculated?
This tool uses the Widmark formula, which estimates blood alcohol from the alcohol consumed, your body weight and sex, and the time since your first drink.
How accurate is a BAC calculator?
It is a rough estimate only. Real BAC depends on food, metabolism, medications, and more, so it can be very different for any individual.
What is the legal driving limit?
In many places it is 0.08 percent, but limits vary by country and can be lower for some drivers. Regardless of any estimate, do not drive after drinking.
How long does alcohol take to leave the body?
Roughly one standard drink per hour, but this varies widely. Only time reduces BAC, not coffee, water, or a cold shower.
Sources
Reviewed against these authoritative references. Last updated August 2026.
- National Institute on Alcohol Abuse and Alcoholism (NIH). What Is A Standard Drink?
- MedlinePlus, U.S. National Library of Medicine. Alcohol
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