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BAC Calculator

Estimate blood alcohol content using the Widmark formula

BAC Calculator

1 standard drink = 12oz beer (5%), 5oz wine (12%), or 1.5oz spirits (40%)

Sex:

Blood Alcohol Content (BAC) measures the percentage of alcohol in the bloodstream. It is calculated using the Widmark formula, which accounts for body weight, sex, number of drinks, and time elapsed. A BAC of 0.08% is the legal driving limit in most US states.

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Tip: BAC calculators estimate — not measure. Actual BAC varies based on medications, food intake, liver health, and individual metabolism. Never rely on a calculation to decide if it is safe to drive.

  1. 1BAC = (drinks × 14g × 0.789) / (weight_kg × distribution_ratio × 1000) × 100
  2. 2Distribution ratio (r): 0.68 for men, 0.55 for women (alcohol distributes into body water)
  3. 3Subtract 0.015% per hour for alcohol metabolized by the liver
  4. 41 standard drink = 14g pure alcohol = 12oz beer / 5oz wine / 1.5oz spirits
160 lb male, 3 drinks in 2 hours=BAC ≈ 0.05%Below legal limit but impaired
130 lb female, 3 drinks in 1 hour=BAC ≈ 0.09%Above legal limit in most jurisdictions
BAC %EffectsLegal status
0.01–0.03Mild relaxation, slight euphoriaLegal everywhere
0.04–0.06Feeling of warmth, lowered inhibitionsLegal (impaired)
0.07–0.09Slight impairment of balance, speechIllegal in most US states
0.10–0.12Significant impairment, slurred speechIllegal everywhere
0.13–0.15Gross motor impairment, blurry visionDangerous
0.16–0.30Nausea, possible blackoutVery dangerous
0.31+Potential loss of consciousnessLife-threatening

Fun Fact

The liver metabolizes approximately 1 standard drink per hour regardless of sex, weight, or coffee intake. Only time reduces BAC — no food, water, or caffeine speeds this up.

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