Time to Sober Calculator

Blood Alcohol Content (BAC) clearance calculations estimate how long it takes for the liver to metabolize alcohol to zero. The liver metabolizes alcohol at a constant rate — it cannot be sped up by coffee, food, water, or sleep.

BAC calculation formula (Widmark formula): BAC = (Alcohol Consumed in grams) ÷ (Body Weight in grams × Distribution Ratio) × 100

Where:

• Distribution Ratio (r): 0.68 for men, 0.55 for women (reflects different body water content)
• Alcohol in grams = Volume of drink (mL) × ABV (%) × 0.789 (density of ethanol)

Standard drink alcohol content:

• Beer (5%, 12 oz / 355 mL): ~14g alcohol
• Wine (12%, 5 oz / 148 mL): ~14g alcohol
• Spirit (40%, 1.5 oz / 44 mL): ~14g alcohol

All standard drinks contain approximately 14 grams of pure alcohol (US standard).

Metabolism rate: The liver eliminates alcohol at approximately 0.015–0.020% BAC per hour (the Widmark elimination constant β).

Time to sober up formula: Hours to Zero = BAC ÷ 0.015

This is the minimum time — the 0.015 rate is conservative; actual rate varies 0.010–0.020 between individuals.

What each variable means:

• BAC 0.08% — the legal driving limit in the US (0.05% in most of Europe and Australia)
• r (distribution ratio) — women have higher BAC per drink due to lower body water fraction and lower levels of alcohol dehydrogenase enzyme
• Food effect — food slows alcohol absorption but does NOT speed metabolism; it lowers peak BAC but doesn’t shorten clearance time

Reference: BAC effects

• 0.02–0.03%: Slight relaxation, mood lift
• 0.05–0.07%: Reduced inhibition, mild impairment
• 0.08%: Legal driving limit; coordination impaired
• 0.10–0.15%: Slurred speech, reaction time severely slowed
• 0.20%+: Severe impairment; blackout possible
• 0.30%+: Loss of consciousness; potentially fatal

Worked example: 170-lb man (77 kg) consumes 4 standard drinks over 2 hours.

Alcohol = 4 × 14g = 56g Body weight = 77 kg = 77,000 g Peak BAC = 56 ÷ (77,000 × 0.68) × 100 = 56 ÷ 52,360 × 100 = 0.107%

Metabolism over 2 hours = 2 × 0.015 = 0.030 BAC at end of drinking = 0.107 − 0.030 = 0.077% (just below legal limit — but still impaired)

Hours remaining to zero: 0.077 ÷ 0.015 = 5.1 additional hours to fully sober up.