BAC Calculator: Estimate Blood Alcohol Content and Sobriety Time

How to use the tool

• Select gender – pick “Male” or “Female.”
  Example inputs: Non-binary users can choose the closer match; assume “Female” if unsure.
• Enter weight – choose pounds or kilograms.
  Sample 1: 140 lbs
  Sample 2: 82 kg
• Add number of standard drinks – round halves allowed.
  Sample 1: 5 drinks (e.g., four beers, one shot)
  Sample 2: 2.25 drinks (one pint of craft beer plus a small wine)
• Hours since first drink – use decimals for fractions.
  Sample 1: 2 h
  Sample 2: 1.25 h
• Hit “Calculate” – the app returns Estimated BAC, hours to zero, and a line graph of decline.

Formula behind the result

$$BAC = rac{A \times 5.14}{W \times r} – 0.015 \times H$$

• A = drinks × 0.6 oz pure alcohol
• W = body weight in pounds
• r = 0.73 (male) or 0.66 (female)
• H = hours since first drink

Worked Example A

• Female, 140 lbs, 5 drinks, 2 h
• A = 5 × 0.6 = 3 oz
• BAC = ((3×5.14)/(140×0.66)) – 0.03 ≈ 0.137 %
• Time to zero = 0.137 / 0.015 ≈ 9.1 h

Worked Example B

• Male, 80 kg (176 lb), 3.5 drinks, 1 h
• A = 3.5 × 0.6 = 2.1 oz
• BAC = ((2.1×5.14)/(176×0.73)) – 0.015 ≈ 0.069 %
• Time to zero = 0.069 / 0.015 ≈ 4.6 h

Quick-Facts

• Standard drink = 14 g (0.6 oz) pure alcohol (NIAAA, 2021).
• Average metabolic clearance = 0.015 % BAC per hour (CDC, 2022).
• U.S. legal driving limit = 0.08 % BAC (NHTSA, 2023).
• “Women reach higher BAC than men after identical drinks” (WHO Global Status Report on Alcohol, 2018).
• One 12 oz 5 % beer equals roughly 1 standard drink (NIH Alcohol Facts, 2022).

FAQ

What is BAC?

Your Blood Alcohol Content shows percent alcohol in blood; 0.08 % means 0.08 g per 100 mL (NHTSA, 2023).

How precise is this calculator?

It uses average metabolic rates; actual BAC varies with genetics, food, and medication (NIAAA, 2021).

Why choose gender?

Body-water ratio differs—0.73 for men, 0.66 for women—changing dilution of alcohol (WHO, 2018).

Does drink type matter?

Only alcohol amount counts; a 5 oz 12 % wine matches a 1.5 oz 40 % shot at 0.6 oz ethanol (NIH, 2022).

Can coffee sober me?

No. “Time is the only cure for intoxication” (CDC, 2022).

How long until I’m safe to drive?

Divide current BAC by 0.015; 0.09 % needs about 6 h (CDC, 2022).

Will eating lower BAC?

Food slows absorption, producing a lower peak but doesn’t speed elimination (NIAAA, 2021).

Do medications change results?

Some drugs boost alcohol’s effect or slow metabolism; consult your pharmacist (FDA Drug Safety, 2023).