ZOVATOOL

BAC Calculator

Drinks
Current BAC (Widmark + elimination)
0.000%
Within limits
Peak BAC (Widmark)
0.027%
Peak BAC (Watson TBW)
0.243%
Total alcohol
14.0 g
Stage
Subclinical
Hours to sober
1.8 h
from peak, β=0.015/h
⚠ Estimates only. Never drive after drinking. Tolerance, medications, metabolism, and health conditions all change BAC significantly.

How to use the BAC Calculator

  1. Enter body weight and sex (Widmark's formula uses different distribution ratios: 0.68 male, 0.55 female).
  2. Add drinks — beer (12 oz, 5%), wine (5 oz, 12%), spirits (1.5 oz, 40%), or custom.
  3. Enter time elapsed since first drink.
  4. Calculator returns current estimated BAC.
  5. Compare against legal driving limits (US 0.08%, UT 0.05%, Europe 0.05%, Japan 0.02%).
  6. See estimated time until BAC returns to 0.00% (about 0.015%/hour elimination).
  7. Track BAC across time — see peak and decline curve.
  8. Add food consumed for slower absorption estimate (food delays peak by 30–60 min).
  9. Save session to review the next day.
  10. NEVER use this calculator to decide if you can drive — estimates only.
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Blood Alcohol Concentration: what the number really means and its limits

Blood Alcohol Concentration (BAC) measures grams of alcohol per 100 mL of blood, expressed as a percentage. The US legal driving limit is 0.08% (0.04% for commercial drivers, effectively 0% under age 21). Utah lowered its limit to 0.05% in 2019 — matching most of Europe, Canada and Australia. Some countries go stricter: Japan, Norway, Sweden, Poland at 0.02%.

The BAC calculator applies Widmark's formula (1932), the 90-year-old foundation of forensic alcohol calculation: BAC = (grams of alcohol × 100) ÷ (body weight in grams × distribution ratio) − 0.015 × hours since drinking started. Distribution ratio is 0.68 for men and 0.55 for women — women have proportionally more fat and less water than men of the same weight, so alcohol distributes into a smaller water pool, producing higher BAC per drink.

The physiology matters. Alcohol absorbs from the stomach (20%) and small intestine (80%). Empty stomach: peak BAC in 30–45 minutes. With food: peak in 60–90 minutes and 20–30% lower than empty-stomach peak. Elimination is roughly linear at 0.015% per hour — about one standard drink per hour. Coffee, cold showers, exercise and vomiting do NOT speed elimination. Only time works.

A standard drink varies by country. US: 14 g of pure alcohol = 12 oz beer at 5% ABV = 5 oz wine at 12% = 1.5 oz spirits at 40%. UK standard: 8 g. Australia: 10 g. Restaurant pours in real life almost always exceed 'standard' — a generous restaurant wine pour can be 6–8 oz (well over one standard drink). Craft beers at 7–9% ABV pack 1.5–2× the alcohol of a standard beer. Underestimating drinks is how people cross the legal limit thinking they've had two.

The critical caveat: BAC calculators are estimates only. Actual BAC varies with gastric emptying rate (food, medications), enzyme genetics (ALDH2 variants slow metabolism, common in East Asians), fatigue, dehydration, and combined use of other CNS depressants. Never use a calculator's output to decide whether you can drive. If you've had any alcohol within two hours, the safest answer is: don't. Breathalyzers are more accurate; blood tests are the legal-standard proof. Use the calculator to understand impact, plan pace and know when you'll be safe to drive next morning — not to push right up to the legal limit.