About BAC Levels
Why This Tool Exists
Most people have no idea what their blood alcohol content actually is after a few drinks. They guess. They go by feel. And "feeling fine" at 0.10% BAC — well above the legal limit — is dangerously common.
BAC Levels exists to close that gap between perception and reality. We built a calculator that gives you a reasonable estimate in seconds, right from your phone, so you can make a more informed choice about whether to drive, wait, or call a ride.
We are not anti-alcohol. We are anti-guessing.
Our Methodology
Every BAC calculation on this site uses the Widmark formula, developed by Swedish chemist Erik Widmark in the 1930s. Despite its age, it remains the standard method used by forensic toxicologists, law enforcement agencies, and medical professionals worldwide.
The formula works by calculating the theoretical amount of alcohol distributed through your body water, then subtracting the amount your liver has metabolized over time. The key variables are:
- Alcohol consumed — measured in standard drinks (14 grams of pure alcohol each)
- Body weight — heavier individuals have more body water to dilute alcohol
- Biological sex — the Widmark "r" factor accounts for differences in body water percentage (0.68 for males, 0.55 for females on average)
- Time elapsed — alcohol is eliminated at approximately 0.015% BAC per hour
- Food intake — eating slows absorption, reducing peak BAC
The elimination rate of 0.015% per hour represents a well-documented average. Individual rates range from 0.010% to 0.020% depending on liver health, genetics, and other factors. Our calculator uses the average — your actual rate may differ.
What This Tool Cannot Do
No calculator can replace a breathalyzer. The Widmark formula provides estimates based on population averages. It cannot account for:
- Your individual metabolism and liver function
- Medication interactions (antihistamines, antidepressants, pain medications, and many others interact with alcohol)
- Health conditions affecting alcohol processing
- Genetic variations in alcohol dehydrogenase enzymes
- Exact alcohol content of your specific drinks (a "beer" can be 3.5% or 12% ABV)
- Hydration level, fatigue, or sleep deprivation
We display this limitation prominently on every page. If there is any doubt about whether you should drive, the answer is already clear — don't.
Data Sources & References
- Widmark, E.M.P. (1932). Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung. Berlin: Urban & Schwarzenberg.
- National Highway Traffic Safety Administration (NHTSA) — DUI statistics and BAC limit data
- National Institute on Alcohol Abuse and Alcoholism (NIAAA) — standard drink definitions
- Substance Abuse and Mental Health Services Administration (SAMHSA) — helpline: 1-800-662-4357
Privacy by Design
Every calculation happens entirely in your browser. Zero data is sent to our servers. Your weight, gender, and drink history never leave your device — they are stored only in your browser's local storage and can be cleared at any time.
We use Google Analytics and Microsoft Clarity to understand site usage patterns (which pages are visited, how long). These tools never see your BAC results or personal inputs.
Available Tools
- BAC Calculator — estimate your blood alcohol content based on drinks, weight, time
- BAC Chart — reference table by weight and number of drinks
- Standard Drinks Calculator — convert any drink to standard drink equivalents
- Sober Calculator — estimate when you will be under the legal limit or fully sober
- ABV Calculator — alcohol by volume tools for homebrewers
- Alcohol Calorie Calculator — track calories from drinking
- Legal BAC Limits by State — DUI laws across all 50 US states
All tools are free, work on any device, and require no sign-up or download.
Contact
Questions, feedback, or corrections: [email protected]
If you or someone you know needs help with alcohol, call SAMHSA's free, confidential helpline: 1-800-662-4357 (available 24/7).