Blood Alcohol Content (BAC) Calculator
Estimate your blood alcohol content based on drinks, body weight, sex and time. An educational estimate only — never use it to decide whether to drive.
1 standard drink = 14g alcohol (a 350ml beer, 150ml wine, or 45ml spirit)
An important safety note
This calculator provides a rough educational estimate only. Real blood alcohol content depends on many individual factors this tool cannot capture — your metabolism, food eaten, medications, hydration, health conditions, the exact alcohol content of your drinks and more. The only accurate way to measure BAC is with a breathalyser or blood test. You should never use this or any online estimate to decide whether it is safe to drive. If you have consumed any alcohol, the safest choice is always not to drive.
What is blood alcohol content?
Blood alcohol content, or BAC, is the percentage of alcohol in your bloodstream. A BAC of 0.08% means 0.08 grams of alcohol per 100 millilitres of blood, which is the legal driving limit in many countries — though numerous countries set lower limits, and some have zero-tolerance laws. Even well below these limits, alcohol impairs judgement, coordination and reaction time. Impairment begins with the very first drink, long before any legal threshold is reached.
How BAC is estimated
This calculator uses a version of the Widmark formula, which estimates BAC from the amount of alcohol consumed, your body weight, your sex and the time elapsed. Sex matters because of differences in average body water content. Your body metabolises alcohol at a roughly steady rate — about 0.015% BAC per hour — which is why time since your first drink reduces the estimate. However, nothing speeds this up: not coffee, cold showers or food. Only time lowers your BAC.
Drinking responsibly
If you choose to drink, doing so in moderation and never before driving or operating machinery protects you and others. Plan ahead with a designated driver, taxi or public transport. Be aware that one standard drink is a specific amount, and many served drinks contain more than one. Alcohol affects everyone differently, and the only truly safe BAC for driving is zero. If you are concerned about your drinking, a doctor or support service can help.
Frequently Asked Questions
No. This is an educational estimate only and can be significantly inaccurate for any individual. The only reliable measure is a breathalyser or blood test. If you have consumed any alcohol, the safest decision is always not to drive. Never rely on an online estimate for that choice.
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Sources & References
- 1.Widmark EMP.. Principles and applications of medicolegal alcohol determination.
- 2.U.S. National Highway Traffic Safety Administration (NHTSA). The ABCs of BAC.
- 3.World Health Organization. Global status report on alcohol and health.
LifeCheckIQ content is based on peer-reviewed research, recognised clinical guidelines, and authoritative medical sources, and is reviewed by Deborah Adotso, General Nurse, for clinical accuracy.
Medical Disclaimer: This tool is for informational and educational purposes only. Results are not a medical diagnosis. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment. In an emergency, call your local emergency number or visit the nearest hospital immediately.