Health & Fitness

Blood Alcohol Content Calculator | BAC, Widmark Formula & Sobriety Timeline

Estimate blood alcohol content using the Widmark formula. Track drinks over time by type and strength, see a live BAC elimination curve, and calculate exactly when BAC drops below 0.08% (legal limit) and 0.00% (fully sober). Not a substitute for a breathalyzer.

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Educational estimate only — not a substitute for a certified breathalyzer.

BAC varies with food intake, hydration, medications, and individual metabolism. Never drive if you have consumed alcohol.

Biological Sex

Body Weight

Started drinking how long ago (hrs)

Time since first drink, now = 0

Drinks Consumed

What Is the Blood Alcohol Content Calculator | BAC, Widmark Formula & Sobriety Timeline?

The Widmark formula, developed by Swedish physician Erik Widmark in 1932, is the foundation of forensic alcohol calculations used by law enforcement and medical professionals. It estimates blood alcohol concentration based on the amount of alcohol consumed, body weight, biological sex, and elapsed time. This calculator is for educational purposes — a certified breathalyzer or blood test is the only legally recognized measure.

›Why sex affects BAC. Women typically have less body water per unit of body weight and lower levels of the enzyme alcohol dehydrogenase. The Widmark r-factor accounts for this: 0.73 for males, 0.66 for females.
›The 0.015 elimination constant. The liver metabolizes alcohol at approximately 0.015% BAC per hour regardless of how much has been consumed. Coffee, food, exercise, and cold water do not accelerate this rate — only time does.
›What the Widmark formula cannot account for. Food consumption (slows absorption), medication interactions, tolerance, hydration level, liver health, and the exact rate of consumption over time. These can shift actual BAC by ±30%.
›Legal limits vary by country. The US and UK: 0.08%. EU (most countries): 0.05%. Sweden: 0.02%. Some US states have zero tolerance for drivers under 21. Commercial drivers: 0.04%.

Formula

Widmark Formula

BAC = (A × 5.14 / W × r) − 0.015 × H

where A = total oz of pure alcohol, W = body weight in lbs

r = Widmark factor (0.73 male, 0.66 female), H = hours since drinking began

Pure Alcohol Content

oz pure alcohol = volume (oz) × ABV (%/100)

Example: 12 oz beer at 5% = 12 × 0.05 = 0.6 oz pure alcohol

Elimination Rate

BAC decreases at approximately 0.015% per hour

Hours to sober = BAC / 0.015

How to Use

1
Select biological sex and enter body weight in lbs or kg.
2
Enter how many hours ago you started drinking.
3
Add each drink type and quantity. Use presets or enter custom ABV and volume.
4
Click Estimate BAC to see your estimated blood alcohol level.
5
Review the BAC category, time to reach the legal limit, and time to full sobriety.
6
This tool is educational only — never use it to decide whether to drive.

1
Enter personal details: Select biological sex and enter body weight. These two variables have the largest impact on BAC calculation.
2
Set drinking start time: Enter how many hours ago you started drinking. If you started 2 hours ago and are still drinking, enter 2.
3
Add drinks: Select drink types from the presets (beer, wine, spirits, cocktail) or choose Custom to enter exact volume and ABV. Enter the number of each drink consumed.
4
Click Estimate BAC: The calculator applies the Widmark formula and shows your current estimated BAC, its category, and the elimination timeline.
5
Review the BAC chart: The chart shows the elimination curve from now until sobriety. The red dashed line is the 0.08% US legal driving threshold.

Example Calculation

Example: 175 lb male, 3 beers + 1 glass of wine over 2 hours

3 × regular beer (12 oz, 5%) = 3 × 0.60 oz = 1.80 oz pure alcohol

1 × wine (5 oz, 12%) = 0.60 oz pure alcohol

Total pure alcohol A = 2.40 oz

BAC = (2.40 × 5.14) / (175 × 0.73) − 0.015 × 2

BAC = 12.336 / 127.75 − 0.030 = 0.0966 − 0.030 = 0.0666%

Estimated BAC: 0.067% — below US legal limit of 0.08%

Hours to full sobriety: 0.067 / 0.015 ≈ 4.5 more hours

Understanding Blood Alcohol Content | BAC, Widmark Formula & Sobriety Timeline

Why BAC Is Not Linear

Most people assume BAC rises in a smooth straight line while drinking and then falls in a straight line afterward. In reality, alcohol absorption is slower than elimination for the first 30–90 minutes after a drink, meaning your BAC continues rising for up to an hour after your last drink — even after you stop. This is why someone who stops drinking at what feels like a safe level may reach their actual peak BAC while driving home.

The 0.08% Limit Is a Legal Threshold, Not a Safety Threshold

Research consistently shows impaired driving ability at BAC levels well below 0.08%. Reaction time slows, attention divides less effectively, and risk assessment becomes overconfident starting around 0.02–0.04% BAC. The 0.08% legal limit represents the political compromise between detection reliability and public safety, not the point at which driving ability is unimpaired.

›0.02–0.03%: mild relaxation, slight impairment in divided attention tasks
›0.04–0.06%: noticeable impairment in judgment and coordination; legally impaired in many EU countries
›0.07–0.09%: legally impaired in the US; significant reaction time reduction
›0.10–0.15%: clearly drunk; major impairment in balance, speech, and decision-making

Frequently Asked Questions

How accurate is the Widmark formula compared to a breathalyzer?

Widmark formula accuracy: ±15–30%. Food, rate of consumption, and individual metabolism are the biggest sources of error. Never use a calculator result to make a legal driving decision.

Does eating food really slow down BAC that much?

Food reduces peak BAC by 30–50% by slowing absorption. The calculator does not model food consumption, so it may overestimate BAC for someone who drank with a meal.

Can I speed up the elimination of alcohol?

Nothing speeds up alcohol metabolism — only time works. Coffee makes you alert but still drunk. The 0.015%/hr elimination rate is fixed by liver enzyme capacity.