BAC Calculator & Estimator
Estimate your Blood Alcohol Content (BAC) instantly. Free, easy-to-use tool based on the Widmark formula, factoring in weight, gender, units, and time.
Calculate Your Blood Alcohol Content
Enter your details below to get an instant, estimated BAC percentage and check it against UK legal driving limits.
Personal Details
Enter your metrics to calculate estimated BAC
BAC Results
Estimated based on the Widmark formula
BAC Levels & Typical Effects
Understanding how different Blood Alcohol Content levels affect the body and their legal status in the UK.
| BAC (%) | mg/100ml | Typical Effects | UK Legal Status |
|---|---|---|---|
| 0.00% | 0 mg | Normal behaviour, no impairment | Legal |
| 0.01% – 0.04% | 10 – 40 mg | Mild relaxation, slight mood elevation | Legal |
| 0.05% – 0.07% | 50 – 70 mg | Reduced coordination, impaired judgment | Over Scotland Limit |
| 0.08% – 0.14% | 80 – 140 mg | Significant impairment, slowed reaction time | Over UK Limit |
| 0.15% – 0.29% | 150 – 290 mg | Severe impairment, nausea, potential blackout | Over UK Limit |
| 0.30%+ | 300+ mg | Loss of consciousness, risk of alcohol poisoning | Medical Emergency |
BAC Calculator FAQ
Everything you need to know about blood alcohol content, legal limits, and how the body processes alcohol.
In England, Wales, and Northern Ireland, the legal blood alcohol limit for drivers is 80 milligrams of alcohol per 100 millilitres of blood (0.08%). In Scotland, the limit is strictly lower at 50 milligrams per 100 millilitres (0.05%).
The Widmark formula estimates BAC by dividing the total grams of alcohol consumed by the product of body weight (in grams) and a gender-specific distribution ratio (0.68 for men, 0.55 for women). It then subtracts the alcohol eliminated over time (approximately 0.015% per hour).
No. Only time can lower your Blood Alcohol Content. The liver metabolises alcohol at a relatively constant rate of about one UK unit per hour. Coffee, cold showers, or exercise may make you feel more alert, but they do not speed up the elimination of alcohol from your bloodstream.
A standard UK unit contains 10 millilitres (or 8 grams) of pure alcohol. For example, a typical pint of average-strength beer (4% ABV) contains about 2.3 units, while a standard 175ml glass of wine (12% ABV) contains about 2.1 units.