BAC Calculator
Estimate your Blood Alcohol Content (BAC) using the Widmark formula. For educational purposes only — never drink and drive.
| BAC Range | Effects | Status |
|---|---|---|
| 0.01 – 0.03% | Subtle mood elevation, slight warmth | Subtle |
| 0.03 – 0.06% | Mild relaxation, lowered inhibitions | Mild |
| 0.06 – 0.10% | Impaired judgment & coordination | Impaired |
| 0.10 – 0.20% | Slurred speech, staggering, nausea | Drunk |
| 0.20 – 0.30% | Severe impairment, blackout risk | Dangerous |
| > 0.30% | Life-threatening, coma risk | Critical |
Estimate your Blood Alcohol Content (BAC) from the drinks you've had, your body weight, and time elapsed, using the widely cited Widmark formula. For educational purposes only.
How BAC Calculator Works
The Widmark formula estimates BAC as: (ounces of pure alcohol consumed × 5.14) ÷ (body weight in lbs × distribution ratio) − (0.015 × hours elapsed). The distribution ratio (0.73 for men, 0.66 for women) reflects that alcohol distributes through body water, and women's bodies typically have a somewhat higher proportion of body fat to water than men's at the same weight — which is why the same amount of alcohol tends to produce a higher BAC for a woman than a man of equal weight.
Pure alcohol content is calculated from each drink type's typical volume and alcohol-by-volume percentage — a standard 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, and a 1.5 oz shot at 40% ABV — then summed into total ounces of alcohol and standard drink equivalents (1 standard drink ≈ 0.6 oz of pure alcohol).
The 0.015 per hour subtraction reflects the commonly cited average rate at which the body metabolizes alcohol, which the calculator also uses separately to estimate roughly how many hours remain until BAC returns to zero from its calculated peak.
See It In Action
Who Uses BAC Calculator and Why
- Understanding, for educational purposes, roughly how factors like weight, drink type, and time affect estimated BAC.
- Seeing how standard drink equivalents (beer, wine, spirits) add up in terms of pure alcohol content.
- Getting a rough estimate of how many hours it might take for BAC to return to zero after a set of drinks.
Mistakes to Avoid
- Using this tool's estimate to decide whether it's safe to drive — the calculator itself is explicit that this is for educational purposes only and should never be used to make that decision, since real impairment can begin well below the legal BAC limit.
- Ignoring real-world factors the Widmark formula can't account for, like food in your stomach, medications, hydration, and individual metabolism — all of which meaningfully shift actual BAC away from the formula's prediction.
- Assuming the same drink count produces the same BAC for two people of different sexes at the same weight — the formula intentionally uses different distribution ratios for men and women, so this difference is expected, not an error.
Tips for Best Results
- Use the standard drink equivalents shown for each drink type to get a rough sense of total alcohol consumed, since actual pour sizes and ABV percentages vary a lot in practice.
- If you've had any alcohol at all, arrange alternate transportation rather than referencing any calculator's estimate — this tool is not a substitute for a breathalyzer or a safety decision-making tool.
Fixing Common Problems
My estimated BAC seems lower than how impaired I actually feel. — The Widmark formula is an approximation and doesn't account for food intake, medications, individual metabolism, or hydration — always trust how you actually feel over a calculated estimate, and never use this tool to judge whether it's safe to drive.
Terms Explained
Widmark formula: A long-established formula estimating blood alcohol content from alcohol consumed, body weight, a sex-specific distribution ratio, and time elapsed since drinking began.
Standard drink: A reference unit of alcohol content (about 0.6 oz of pure alcohol) used to compare different drink types and sizes on a consistent scale.