Alcohol (BAC) Calculator
Estimate Blood Alcohol Content (BAC) using the Widmark formula based on drinks consumed, body weight, gender, and hours since drinking.
About the Alcohol (BAC) Calculator
Blood Alcohol Content (BAC) measures the concentration of alcohol in the bloodstream, expressed as a percentage. A BAC of 0.08% means 0.08 grams of alcohol per 100 millilitres of blood — the legal driving limit in most US states, the UK (for England and Wales), and many other countries. Even low BAC levels affect reaction time, judgment, and coordination, which is why 'drink-drive' limits are not a safety guarantee but a legal minimum.
The Widmark formula is the most widely used method for estimating BAC: BAC = (alcohol consumed in grams) / (body weight in grams × Widmark distribution factor) − (elimination rate × hours). The Widmark factor is approximately 0.68 for men and 0.55 for women, reflecting differences in body water percentage and enzyme activity. The standard alcohol elimination rate is approximately 0.015% BAC per hour for most people.
This calculator is for educational purposes only. Actual BAC varies significantly based on metabolism, food consumption, medications, liver health, and other individual factors. Do not use this calculator to determine whether it is safe to drive — if you have consumed alcohol, arrange an alternative way home.
How Alcohol Affects the Body
Alcohol (ethanol) is absorbed into the bloodstream primarily through the small intestine. Absorption begins within minutes of drinking and is largely complete within 30–60 minutes on an empty stomach. Food in the stomach slows absorption significantly — eating before or during drinking keeps BAC lower and peaks later than drinking on an empty stomach. High-fat foods are particularly effective at slowing alcohol absorption.
At low BAC levels (0.02–0.05%), most people experience mild relaxation, reduced inhibitions, and slightly impaired fine motor control. At 0.05–0.08%, judgment is noticeably impaired, reaction time slows, and the ability to track moving objects decreases. At 0.08–0.15%, significant motor impairment, slurred speech, and severely compromised decision-making occur. Above 0.15%, the risk of alcohol poisoning, loss of consciousness, and respiratory depression increases sharply.
The liver metabolises alcohol at a roughly constant rate of about one standard drink per hour (approximately 10g of pure alcohol) for most people. There is no reliable way to speed up this process — coffee, cold showers, food, or exercise do not accelerate alcohol metabolism. The only reliable way to lower BAC is time. Planning sober transportation before drinking begins is the only effective harm-reduction strategy.