How BAC Is Estimated
The Widmark formula estimates BAC from number of drinks, body weight, sex-based distribution ratio, and time elapsed. Men distribute alcohol across about 68% of body weight; women across about 55%. This is why—at equal weight and equal drinks—women reach a higher BAC.
BAC = (Drinks × 0.6 × 5.14 / (Weight × r)) − (0.015 × Hours)
r = 0.73 (male) or 0.66 (female)
BAC Levels and Effects
| BAC % | Typical Effects | Legal Status |
|---|---|---|
| 0.02-0.03% | Mild relaxation, slight mood elevation | Legal |
| 0.04-0.06% | Lowered inhibitions, impaired judgment | Legal but impaired |
| 0.07-0.09% | Reduced coordination, slurred speech | At or over limit |
| 0.10-0.12% | Significant motor impairment, poor judgment | Illegal to drive |
| 0.13-0.15% | Blurred vision, anxiety, lack of balance | Seriously impaired |
| 0.16-0.20% | Nausea, feeling dazed | Dangerously impaired |
| 0.25+ | Risk of passing out, choking | Medical emergency risk |
| 0.35+ | Potential coma or death | Life-threatening |
What Counts as a Standard Drink
One standard drink contains 14g (0.6 oz) of pure alcohol:
- 12 oz regular beer (5% ABV)
- 5 oz wine (12% ABV)
- 1.5 oz spirits (40% ABV / 80 proof)
A pint of craft IPA at 7.5% ABV is about 1.9 standard drinks. A large wine glass with 8 oz is about 1.6 standard drinks. Most people undercount because serving sizes exceed these standards.
Factors That Affect BAC
Food: Eating slows absorption but doesn't reduce total alcohol absorbed. A full stomach delays the peak BAC by 1-2 hours.
Tolerance: Regular drinkers feel less impaired at the same BAC, but their actual impairment is the same. Tolerance does not change how fast alcohol is metabolized.
Medications: Many medications interact with alcohol and amplify its effects. Antihistamines, antidepressants, and painkillers are common offenders.