How accurate is the Widmark formula?

Widmark gives a useful estimate but is not legally definitive. Individual variation in metabolism, food intake, hydration, body composition and medication can shift true BAC by ±20–30%.

How long does alcohol take to leave the system?

The body metabolises about 0.015% BAC per hour. A peak BAC of 0.08% takes approximately 5.3 hours to fully clear. Coffee, cold showers and food do not speed this up.

Is this a substitute for a breath or blood test?

No. Use as an educational guide only. If your BAC matters legally or medically, use a certified breathalyser or blood test.

🍺 Blood Alcohol Content (BAC) Calculator

Estimate your blood alcohol content using the Widmark formula — the internationally recognised scientific standard. For educational purposes only. Never drive or operate machinery after drinking. All calculations run in your browser — no data stored.

Biological Sex

Unit System

Body Weight (kg)

Hours Since First Drink

DRINKS CONSUMED

🍺 Beer / Cider (pint, 4.5%)

🍷 Wine (175ml glass, 13%)

🥃 Spirits (25ml shot, 40%)

🍹 Cocktails (avg. 1.5 units each)

⚠️ IMPORTANT: This calculator is for educational purposes only. BAC estimates are highly variable and depend on factors this tool cannot account for (food intake, medications, health conditions, hydration). Never drive after drinking, regardless of what this calculator shows. The only safe BAC for driving is 0.00%.

About This Calculator

The BAC Calculator uses the Widmark formula — the scientific standard for estimating blood alcohol concentration — developed by Swedish physician Erik Widmark in the 1920s and still used by forensic and medical experts today.

The Widmark Formula

BAC (%) = (Alcohol consumed in grams ÷ (Body weight in grams × Gender constant r)) − (Metabolism rate × Hours)

r (distribution ratio): 0.68 for males, 0.55 for females (reflects different body water percentages)
Metabolism rate: 0.015% BAC per hour (average adult liver elimination rate)

BAC Level Reference Guide

0.00–0.02%: No notable impairment for most people
0.02–0.05%: Mild relaxation, slight impairment of judgment
0.05–0.08%: Reduced coordination, slower reaction times — illegal to drive in most of Europe
0.08–0.15%: Significant impairment — slurred speech, balance problems
0.15–0.30%: Severe impairment, high risk of blackout
Above 0.30%: Risk of alcohol poisoning — medical emergency

Legal Driving Limits

Ireland, Germany, France, Spain, Netherlands: 0.05%
Czech Republic, Hungary, Slovakia, Romania: 0.00%

⚠️

Important Note: This tool is intended to provide estimates and should not be used as a substitute for professional advice. BAC varies significantly based on food intake, medications, individual metabolism, and health status. Never rely on this calculator to make decisions about driving or operating machinery. If in doubt, don't drive.

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