BAC Calculator – Estimate Blood Alcohol Concentration
BAC Calculator
Estimate your Blood Alcohol Concentration (BAC) and find out how long it will take for your body to process the alcohol.
• 12 oz of regular beer (5% ABV)
• 5 oz of table wine (12% ABV)
• 1.5 oz of distilled spirits/liquor (40% ABV)
Quick answer
A BAC calculator estimates your blood alcohol concentration, the percentage of alcohol in your bloodstream. Enter your biological sex, body weight, the hours since your first drink and the number of standard drinks, then click Calculate BAC. The tool shows an estimated BAC, a status such as Impaired (Caution), and roughly how many hours until your BAC returns to zero.
Our free BAC calculator uses the Widmark formula, the classic equation used in alcohol research and education. It supports pounds and kilograms and explains what a standard drink means.
Important: a BAC calculator gives an estimate only. Food, medication, genetics, health and the actual strength of your drinks all change real BAC. Never use this or any online BAC calculator to decide whether you are safe to drive, ride, swim or operate machinery. If you have been drinking, do not drive.
How the BAC Calculator Works
The Widmark formula estimates BAC from the alcohol you drank, your body weight and a body water constant, then subtracts the alcohol your liver has processed over time:
- BAC = (alcohol in oz × 5.14 ÷ (body weight in lb × r)) − 0.015 × hours
- r = 0.73 for men and 0.66 for women (body water distribution)
- One standard drink ≈ 0.6 oz (14 g) of pure alcohol
- The body clears roughly 0.015% BAC per hour
Example: an 80 kg man who has had 3 standard drinks over 2 hours has an estimated BAC of about 0.042%, and it would take roughly 2.8 more hours to reach zero.
BAC Levels and Typical Effects
| BAC | Status in tool | Typical effects |
|---|---|---|
| 0.000% | Sober | No alcohol in the blood |
| 0.001% to 0.039% | Slight impairment | Relaxation, mild loss of judgement |
| 0.040% to 0.079% | Impaired (caution) | Reduced coordination and reaction time |
| 0.080% to 0.249% | Legally intoxicated in many places | Clear impairment of balance, speech and judgement |
| 0.250% and above | Extreme danger | Risk of alcohol poisoning, loss of consciousness |
Legal driving limits differ by country, and many places use lower limits such as 0.05% or zero tolerance for new and commercial drivers.
How to Use the BAC Calculator
Here is how to use the BAC calculator.
Step 1: Choose Units, Biological Sex and Weight
Pick Imperial (lbs) or Metric (kg), choose Male or Female and enter your body weight.
Step 2: Enter Hours Since Your First Drink and Number of Drinks
Type how many hours have passed since your first drink and how many standard drinks you have had.
Step 3: Read Your Estimated BAC and Status
Click Calculate BAC. The main card shows your estimated BAC percentage and a coloured status label.
Step 4: See the Time Until Your BAC Reaches Zero
Below the result, Time to Sober shows roughly how many more hours your body needs to clear the alcohol. Only time lowers BAC.
What Counts as One Standard Drink?
- 12 oz (355 ml) of regular beer at about 5% alcohol
- 5 oz (150 ml) of wine at about 12% alcohol
- 1.5 oz (45 ml) of spirits at about 40% alcohol
Many drinks are bigger or stronger than a standard drink. A large glass of wine or a strong craft beer can count as two or more.
Myths About Sobering Up
- Coffee, cold showers and exercise do not lower BAC.
- Eating after drinking does not reverse alcohol already absorbed.
- Feeling fine does not mean your BAC is zero.
- Only time allows the liver to process alcohol.
Why Use a BAC Calculator?
A BAC calculator helps people understand how quickly alcohol builds up and how slowly it leaves the body. It is a useful education tool for responsible drinking and planning, such as deciding to use a taxi or stay over, but it is never a reason to drive after drinking.
Frequently Asked Questions
Is this BAC calculator free?
Yes. It is free and nothing you enter is stored.
How accurate is a BAC calculator?
It gives a rough estimate. Real BAC depends on food, metabolism, medication and drink strength, so it can be higher or lower.
How long does it take for alcohol to leave the body?
On average the body removes about 0.015% BAC per hour, roughly one standard drink per hour.
Can I use this to decide if I can drive?
No. Never use a BAC calculator to decide whether to drive. If you have been drinking, do not drive.
Why do women often have a higher BAC?
On average women have less body water than men of the same weight, so alcohol is more concentrated.
Does coffee lower BAC?
No. Coffee may make you feel more alert, but it does not reduce blood alcohol.