justyourcalculatorBAC Calculator
A rough estimate of blood alcohol content, and when it falls to zero.
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BAC Calculator
Estimate blood alcohol content with Widmark
Estimated BAC
0.055%
Impaired: over the 0.05% limit used in Utah and many countries
- Standard drinks (14 g alcohol each)
- 3
- Pure alcohol
- 42 g
- Peak BAC (before metabolism)
- 0.085%
- Time until about 0.00%
- 3 h 40 min
Never use this to decide whether you can drive. It's a rough estimate: real BAC depends on food, medicines, health and how fast you drank, and you can be impaired well under the legal limit. If you've been drinking, don't drive. Not medical or legal advice.
How it was calculated
- Widmark: BAC = alcohol (g) / (body weight (g) × r) × 100 - 0.015 × hours
- = 42 / (72,575 × 0.68) × 100 - 0.015 × 2 = 0.055%
| BAC | Typical effects |
|---|---|
| 0.02 - 0.03% | Relaxation, mild mood change, slight loss of judgment |
| 0.05 - 0.06% | Lowered alertness, impaired judgment and coordination |
| 0.08% | Legal driving limit in most US states; clearly impaired reaction and control |
| 0.10 - 0.12% | Slurred speech, poor balance and slowed thinking |
| 0.15 - 0.20% | Major loss of balance, vomiting, blackouts possible |
| 0.25 - 0.30% | Confusion, stupor, risk of choking and loss of consciousness |
| 0.35% and up | Coma and risk of death from alcohol poisoning |
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How the bac calculator works
This calculator uses the Widmark formula: BAC (%) = grams of alcohol / (body weight in grams × r) × 100, minus 0.015% for every hour since you started drinking. The factor r is the share of the body that holds water and alcohol: about 0.68 for men and 0.55 for women.
Grams of alcohol = volume in ml × alcohol % × 0.789 (alcohol's density). A US standard drink holds 14 g: a 12 oz beer at 5%, a 5 oz glass of wine at 12% or a 1.5 oz shot of 40% spirits.
The body clears roughly 0.015% BAC an hour, and nothing (coffee, water, a shower) speeds it up. Estimates can be far off for any one person.
Using and checking your result
Published by JustYourCalculator. Check the units and assumptions above, and compare a known example before relying on the output. Calculations use browser arithmetic and may round displayed values.
This tool provides an estimate, not a diagnosis, treatment plan or individualized medical advice. Population formulas may not fit children, pregnancy, athletes or people with health conditions. Discuss health decisions with a qualified clinician.
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