BAC Calculator — Blood Alcohol Content Estimator
Estimate your blood alcohol content (BAC) free using the Widmark formula. Enter weight, gender, drinks and time for instant BAC and sober-up time.
1 standard drink = 12 oz beer / 5 oz wine / 1.5 oz spirit (all ≈ 14g alcohol)
Enter 0 if you are estimating peak BAC
CalcVita. (2026). BAC Calculator — Blood Alcohol Content Estimator. CalcVita. Retrieved June 4, 2026, from https://calcvita.com/en/calculators/bac
Suggested article
Blood Alcohol Content (BAC): How It's Calculated and What It Means
Learn how blood alcohol content is measured, how the Widmark formula works, and what different BAC levels mean for your body and your safety on the road.
Read the full article →How does the BAC calculator work?
Enter your body weight, sex, drink type, number of drinks, and hours since you started drinking. The calculator applies the Widmark formula — the standard forensic toxicology method since 1932 — to estimate your current BAC, the time until you reach 0.00 g/dL, and how your BAC compares to legal driving limits in different countries.
The Widmark formula explained
BAC (g/dL) = (alcohol_grams × 100) / (r × body_weight_grams) − β × hours. The Widmark r-factor (0.68 for men, 0.55 for women) represents the fraction of body weight that is water — alcohol only distributes into body water, not fat. β (0.015 g/dL/hr) is the average liver metabolism rate. A US standard drink = 14g pure alcohol (12 oz beer / 5 oz wine / 1.5 oz spirit, all ~5-12-40% ABV respectively).
Global legal limits
Legal BAC limits for driving differ worldwide: 0.00 g/dL (Czech Republic, Hungary, some Asian countries), 0.02 g/dL (Sweden, Norway, Poland — 0.2 promille), 0.05 g/dL (most EU countries, Australia, Spain, France, Germany, Italy), 0.08 g/dL (USA, UK until 2019, Canada, Japan). Scotland and Wales lowered their limit to 0.05 g/dL in 2014. Many countries apply stricter limits for new and professional drivers.
Factors that affect BAC
Several factors influence your BAC beyond weight and gender: food in your stomach (slows alcohol absorption, peak BAC ~20-30 min later), carbonated mixers (speed absorption), fatigue (increases impairment for same BAC), medications (may amplify effects), and tolerance (affects perceived impairment but NOT actual BAC). The liver can only process ~one standard drink per hour regardless of other factors.
Scientific References
- Widmark EMP (1932). Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung. Urban & Schwarzenberg, Berlin.
- Posey DL, Mozayani A (2007). The estimation of blood alcohol concentration. Forensic Science, Medicine, and Pathology 3(3):195–200. PMID 23674337
- Dubowski KM (1985). Absorption, distribution and elimination of alcohol: highway safety aspects. Journal of Studies on Alcohol Suppl 10:98–108. PMID 3870349
- NIAAA. What Is a Standard Drink? National Institute on Alcohol Abuse and Alcoholism, NIH.
- How does the BAC calculator work?
- This calculator uses the Widmark formula, the gold standard in forensic toxicology since 1932. BAC (g/dL) = (alcohol_grams × 100) / (r × body_weight_grams) − 0.015 × hours. Where r is the Widmark distribution factor (0.68 for men, 0.55 for women) and 0.015 g/dL/hour is the average alcohol metabolism rate. A US standard drink contains approximately 14g of pure alcohol.
- What is BAC and why does it matter?
- Blood Alcohol Content (BAC) measures the concentration of alcohol in your blood, expressed in grams per deciliter (g/dL). At 0.08 g/dL — the legal driving limit in the US and UK — most people show impaired judgment, reaction time, and coordination. Even at 0.05 g/dL (EU/Australia limit), driving ability is measurably reduced. At 0.30+ g/dL, loss of consciousness and medical emergency can occur.
- Why do men and women have different BAC levels for the same drinks?
- The Widmark r-factor accounts for differences in body water distribution. Men average r = 0.68 (68% body water) while women average r = 0.55 (55% body water) because women generally have a higher proportion of body fat, which does not absorb alcohol. This means women reach higher BAC levels than men of the same weight drinking the same amount.
- How long does it take to sober up?
- The liver metabolizes alcohol at approximately 0.015 g/dL per hour on average — equivalent to about one standard drink per hour. This rate is relatively constant and is NOT significantly affected by coffee, water, food, exercise, or cold showers. Time to sober up = current BAC ÷ 0.015. For example, a BAC of 0.09 g/dL takes 0.09 ÷ 0.015 = 6 hours to reach 0.00.
- What are the legal BAC limits around the world?
- Legal driving limits vary significantly: 0.08 g/dL (US, UK before 2019, Canada, Japan), 0.05 g/dL (most EU countries, Australia, New Zealand, South Africa), 0.02 g/dL (Sweden, Norway, Poland, Russia), and 0.00 g/dL (Czech Republic, Hungary, some Middle Eastern and Asian countries). Some jurisdictions apply stricter limits for new drivers and professional drivers.
- Is the BAC calculator accurate for driving decisions?
- No. This calculator provides a scientific estimate, but individual results vary significantly based on medication use, food intake, fatigue, tolerance, health conditions, and exact body composition. The only reliable way to know your BAC is a certified breathalyzer or blood test. Never use this calculator to decide whether it is safe to drive — if you have had any alcohol, use a sober driver, rideshare, or public transport.
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