BAC Calculator
Last updated: June 2026 · Free · No sign-up required
Enter values above and click Calculate to see your result instantly.
Quick reference
Approximate BAC effects:
| BAC | Typical effect |
|---|---|
| 0.02% | Slight relaxation, mild impairment |
| 0.05% | Reduced coordination and judgment |
| 0.08% | Legal limit to drive (US) — impaired |
| 0.15% | Major impairment, loss of balance |
monitor_weight A starting point, not a diagnosis
This calculator gives you the same number a clinician would compute by hand from your inputs. It is informational, never a substitute for a doctor. If a result surprises you, write it down and discuss it at your next appointment — that conversation is the goal, not a verdict from a webpage.
science Built from peer-reviewed formulas
Every health calculator on CalcaTools uses an equation from the WHO, NIH, ACOG, CDC, or a published peer-reviewed paper. The exact citation is in the "Formula & methodology" section. We re-check sources quarterly and update the page when guidance changes — the "Last reviewed" date is at the top.
volunteer_activism Designed for real people
Health calculations only help if you can actually use them. We use plain-English labels (no jargon), accept both metric and US units, and show what a "normal" range looks like alongside your result — so you understand what the number means, not just what it is.
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Your weight, height, age, pregnancy details, and any other health input never leave your browser. Calculations run client-side; nothing is logged or stored on our side. We don't want your medical data — we just want the formula to work for you.
Interpretation guide
What affects BAC:
| Factor | Effect |
|---|---|
| Body weight | More weight, lower BAC |
| Sex | Women reach higher BAC per drink |
| Time | BAC falls ~0.015%/hour |
| Food | Slows absorption, lowers peak |
Formula & methodology
Formula: BAC = (A x 5.14 / (W x r)) - (0.015 x H); A = alcohol oz, W = weight lb, r = 0.73 (M)/0.66 (F), H = hours
The calculator estimates blood alcohol content with the Widmark formula from the number of standard drinks, body weight, sex, and time since the first drink. Alcohol distributes through body water, so heavier people and (on average) men reach a lower BAC per drink. The body clears roughly 0.015% BAC per hour. This is an estimate only — never use it to decide whether it's safe to drive.
Authoritative source: CDC