BAC Calculator

Estimate your Blood Alcohol Concentration (BAC) using the Widmark formula. Calculate exact hours until completely sober, check legal driving limits, and view your metabolic timeline.

Estimated Current BAC

0.066%

✓ Under 0.08% US Limit

Time Until 0.00% Sober

4h 25m

Elimination rate: ~0.015% BAC / hour

Total Standard Drinks

4.0 drinks

~14 grams pure ethanol each

Peak BAC Level

0.104%

Theoretical maximum before burn-off

1. Profile & Timeline

2. Drinks Consumed

Quick Answer: How Long Does Alcohol Stay in Your System?

The human body metabolizes alcohol at an average rate of 0.015% BAC per hour (roughly one standard drink every 60–90 minutes). If your BAC reaches the legal driving limit of 0.08%, it takes approximately 5 hours and 20 minutes for your body to return to completely sober (0.00% BAC).

BAC Impairment Stages & Driving Status

0.02% – 0.03%Mild RelaxationSlight warmth & mood elevation
0.04% – 0.07%Lowered InhibitionsReduced reaction speed
0.08% (Legal Limit)Legally IntoxicatedIllegal to drive in US/UK
0.15%+Severe ImpairmentMajor motor loss & blackout risk

Widmark Equation Variables Reference

Standard Beverage TypeVolumeTypical ABV %Pure Ethanol Content
Standard Domestic Beer12 oz (355 mL)5.0%14.0 grams
Table Wine (Red / White)5 oz (148 mL)12.0%14.0 grams
Distilled Spirits / Liquor Shot1.5 oz (44 mL)40.0% (80 Proof)14.0 grams
Craft IPA / High-Gravity Beer16 oz (Pint)7.5%28.0 grams (2 Drinks)

Step-by-Step Case Study: Widmark Calculation Example

Consider John, a 175 lb (79.4 kg = 79,400 grams) male who drinks 3 standard beers (42g alcohol) and 1 shot (14g alcohol) = 56g alcohol total, over 2.5 hours:

  1. Calculate Theoretical Peak BAC:
    Peak BAC = [56g / (79,400g × 0.68)] × 100 = [56 / 53,992] × 100 = 0.104%.
  2. Deduct Liver Metabolism Over 2.5 Hours:
    Metabolic burn-off = 2.5 hours × 0.015%/hr = 0.038% BAC eliminated.
  3. Calculate Current BAC & Sober Time:
    Current BAC = 0.104% - 0.038% = 0.066% BAC.
    Time until 0.00% sober = 0.066 / 0.015 = 4 hours and 24 minutes remaining.

Frequently Asked Questions

What is the legal BAC limit for operating a motor vehicle in the US and UK?
In the United States, the federal legal limit for non-commercial drivers aged 21 and older is 0.08% Blood Alcohol Concentration (BAC) across 49 states (Utah enforces 0.05%, and commercial CDL drivers face a strict 0.04% limit). In the UK, England and Wales set the limit at 0.08% (80mg of alcohol per 100ml of blood), while Scotland and most European countries enforce 0.05% or zero tolerance.
How fast does the human liver eliminate alcohol from the bloodstream?
The human liver metabolizes alcohol at a constant zero-order kinetics rate of approximately 0.015% BAC per hour (equivalent to roughly one standard drink or 10–14 grams of pure ethanol every 60 to 90 minutes). Neither drinking black coffee, taking cold showers, exercising, nor drinking energy drinks can speed up liver enzyme processing.
What defines one 'Standard Drink' in the United States?
In the United States, one standard drink contains approximately 14 grams (0.6 fluid ounces) of pure ethanol: 12 ounces of regular beer (5% ABV), 5 ounces of table wine (12% ABV), or 1.5 ounces (a standard shot) of 80-proof distilled spirits (40% ABV). High-ABV craft beers (7%–9% ABV) often equal 1.5 to 2.0 standard drinks per pint.
Why do women typically reach higher BAC levels than men of equal weight?
Biological sex affects alcohol pharmacokinetics in two ways: 1. Women naturally have a higher average percentage of body fat and lower total body water (r = 0.55 constant vs r = 0.68 for men), causing alcohol to be concentrated in a smaller water volume; and 2. Women produce lower levels of gastric alcohol dehydrogenase (ADH) in the stomach lining, allowing more alcohol to pass directly into the bloodstream.
How does eating food before drinking impact blood alcohol levels?
Consuming a meal rich in proteins, fats, and carbohydrates before drinking delays gastric emptying into the small intestine (where 80% of alcohol absorption occurs). This slows the rate of alcohol entering the bloodstream, reducing peak BAC levels by up to 20% to 30% compared to drinking on an empty stomach.
Can you get a DUI conviction with a BAC below 0.08%?
Yes. In almost all US states, law enforcement officers can arrest and charge drivers with Driving While Impaired (DWI/DUII) if physical field sobriety tests demonstrate diminished driving ability, even if their breathalyzer score is between 0.01% and 0.07%.
How does the Widmark Formula calculate Blood Alcohol Concentration?
Developed by Swedish forensic chemist Erik Widmark, the formula is: BAC = [Alcohol consumed (grams) / (Body Weight (grams) × r)] × 100 - (Beta × Hours elapsed). The constant 'r' represents gender water distribution (0.68 for males, 0.55 for females) and 'Beta' represents the hourly metabolic burn-off rate (0.015%/hr).

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