BAC Calculator

Estimate your Blood Alcohol Content (BAC) using the Widmark formula. Enter drinks, weight, gender, and time elapsed for a safe-driving guide.

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Disclaimer: This is an estimate only. Do not drive after drinking alcohol regardless of your calculated BAC. Legal limits and individual responses vary. This tool is for educational purposes only.

What Is Blood Alcohol Content (BAC)?

Blood Alcohol Content (BAC) is the concentration of alcohol in your bloodstream, expressed as a percentage. A BAC of 0.05% means there are 0.05 grams of alcohol per 100 millilitres of blood. Even small amounts of alcohol impair reaction time, judgment, and coordination — effects that are dangerous when driving, operating machinery, or making important decisions.

The Widmark Formula

This calculator uses the Widmark formula, the standard method for estimating BAC:

BAC = (Alcohol consumed in grams ÷ (Body weight × r)) × 100 − (0.015 × hours)

r = 0.68 for men, 0.55 for women (body water distribution factor)

Why Women Have Higher BAC Than Men

At the same body weight and alcohol intake, women typically reach higher BAC levels than men. This is primarily because women have a lower proportion of body water (in which alcohol distributes) and lower levels of alcohol dehydrogenase, the enzyme that metabolises alcohol in the stomach.

Frequently Asked Questions

How long does it take for BAC to reach zero?
The body metabolises alcohol at approximately 0.015% BAC per hour. A BAC of 0.08% takes roughly 5–6 hours to reach zero. Coffee, food, and water do not speed this up.
What is a standard drink?
A standard drink contains approximately 14 grams of pure alcohol — equivalent to: 355ml regular beer (5%), 148ml wine (12%), or 44ml spirits (40%).
Is it safe to drive at the legal BAC limit?
Research clearly shows that driving ability is impaired well below the 0.08% legal limit in most countries. The safest choice is not to drive after any amount of alcohol.
Medical Disclaimer: This calculator is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for health decisions.