BAC calculator
Estimate your blood alcohol content (BAC) from what you drank, your weight and time. It is for learning how alcohol builds up, not for deciding anything.
This is an estimate for education only. It cannot tell you if you are safe to drive. If you have been drinking, do not drive.
BAC calculator examples
Sample people, made up to show how the numbers change. Load one into the calculator to tweak it.
Two beers at dinner
Woman, 63 kg (139 lb), 2 beers over 2 hours
Estimated BAC
0.048%
about 48 mg per 100 mL of blood
- Standard drinks
- 2
- Pure alcohol
- 27 g
- What it can feel like
- Relaxed and warm, with some impairment of reasoning and memory.
- This is an estimate, not a measurement. Food, medication, genetics and how fast you drank all change your real BAC.
- BAC can keep rising for a while after your last drink.
- Any alcohol slows reaction time. If you have been drinking, do not drive. Take transit, a cab, or a ride with a sober driver.
A night out
Man, 80 kg (176 lb), 3 beers and 2 shots over 4 hours
Estimated BAC
0.064%
about 64 mg per 100 mL of blood
- Standard drinks
- 5
- Pure alcohol
- 67 g
- What it can feel like
- Relaxed and warm, with some impairment of reasoning and memory.
- This is an estimate, not a measurement. Food, medication, genetics and how fast you drank all change your real BAC.
- BAC can keep rising for a while after your last drink.
- Any alcohol slows reaction time. If you have been drinking, do not drive. Take transit, a cab, or a ride with a sober driver.
Wine with friends
Woman, 70 kg (154 lb), 3 glasses of wine over 3 hours
Estimated BAC
0.060%
about 60 mg per 100 mL of blood
- Standard drinks
- 3
- Pure alcohol
- 40 g
- What it can feel like
- Relaxed and warm, with some impairment of reasoning and memory.
- This is an estimate, not a measurement. Food, medication, genetics and how fast you drank all change your real BAC.
- BAC can keep rising for a while after your last drink.
- Any alcohol slows reaction time. If you have been drinking, do not drive. Take transit, a cab, or a ride with a sober driver.
How the bac calculator works
We use the Widmark formula. Grams of alcohol are divided by your body weight times a body-water factor (0.68 for men, 0.55 for women). Then we subtract 0.015% for each hour.
Drinks are Canada's standard size: 13.45 g of pure alcohol. That is a 341 mL beer at 5%, a 142 mL glass of wine at 12% or a 43 mL shot at 40%.
Real BAC depends on food, medication, genetics, and how fast you drank. Health agencies warn that calculators like this cannot predict your actual level.
Frequently asked questions
How accurate is a BAC calculator?
Not accurate enough to rely on. It shows a typical estimate. Your real BAC can be higher, and it can keep rising after your last drink.
How long does it take for alcohol to leave your body?
On average, BAC drops about 0.015% an hour. Nothing speeds it up: not coffee, water or a cold shower.
What is the legal limit in Canada?
The Criminal Code limit is 80 mg per 100 mL (0.08%), and most provinces have penalties from 50 mg. Impairment starts well before either. If you have been drinking, do not drive.
How many calories are in alcohol?
Alcohol has 7 calories per gram, so one standard drink is about 95 calories before any mix or sugar.
Sources
- Health Canada, Canada's guidance on alcohol and health (standard drink)
- NIAAA, understanding the dangers of alcohol overdose
- Stanford SUPER, what is blood alcohol concentration?
These tools give estimates for healthy adults. They are not medical advice. If you are pregnant, under 18 or managing a health condition, check with your doctor or a registered dietitian.