How this blood alcohol percentage calculator works
This tool estimates your blood alcohol concentration (BAC) using a common Widmark-style formula. It combines how much pure alcohol you consumed, your body weight, your biological sex (as a proxy for body water distribution), and the time since you started drinking.
BAC is shown as a percentage. For example, a BAC of 0.08% means 0.08 grams of alcohol per 100 mL of blood. In many regions, 0.08% is at or above the legal driving limit, but laws vary by country and state.
Formula used
The calculator applies:
BAC = (A × 5.14 / (W × r)) − (0.015 × H)
- A = fluid ounces of pure alcohol consumed
- W = body weight in pounds
- r = alcohol distribution ratio (0.73 male, 0.66 female)
- H = hours since first drink
The metabolism term (0.015 per hour) is a population average. Your personal elimination rate may be faster or slower.
What your BAC result means
- 0.00% – 0.02%: Subtle effects, often hard to notice.
- 0.03% – 0.05%: Mild euphoria, reduced inhibition, lowered alertness.
- 0.06% – 0.07%: Noticeable judgment and coordination decline.
- 0.08% – 0.14%: Significant impairment of reaction time, vision, and control.
- 0.15% – 0.29%: Severe impairment, high risk of injury.
- 0.30%+: Possible loss of consciousness and alcohol poisoning risk.
Even at lower BAC levels, decision-making and motor skills can be affected. If you need to drive or perform safety-sensitive tasks, the safest BAC is 0.00%.
Why real BAC can differ from estimates
Online BAC calculators are useful planning tools, but they cannot account for every factor. Your real BAC can be higher or lower due to:
- How quickly you drank and whether drinks were stronger than expected
- Food intake (especially fat/protein before drinking)
- Hydration status, sleep, stress, and overall health
- Medications and other substances
- Age, genetics, and liver function
Safer drinking tips
- Set a drink limit before going out.
- Alternate alcohol with water.
- Eat before and during drinking.
- Avoid drinking games or rapid consumption.
- Use a designated driver, rideshare, or public transport.
Frequently asked questions
Is this calculator legally accurate?
No. Only certified breath, blood, or urine testing can determine legal intoxication. Treat this page as an educational estimate.
How long until I reach 0.00% BAC?
As a rough rule, many people eliminate about 0.015% BAC per hour. The calculator gives an estimated time, but it is not guaranteed.
Can coffee or a cold shower sober me up?
No. Only time lowers BAC. Caffeine may make you feel more alert, but it does not remove alcohol from your blood.