Blood Alcohol Concentration (BAC) Calculator
Use this tool to estimate your BAC based on body weight, sex, number of standard drinks, and time since your first drink.
Assumes one standard drink contains approximately 0.6 fl oz of pure alcohol and average alcohol elimination of 0.015 BAC/hour.
What Is BAC?
BAC (Blood Alcohol Concentration) is the percentage of alcohol in your bloodstream. A BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood. BAC rises as you drink and falls over time as your body metabolizes alcohol.
BAC is influenced by many factors, including body size, biological sex, drinking speed, food intake, hydration, and individual metabolism. That is why calculator results should be treated as a rough guide rather than exact truth.
How This BAC Calculator Works
This calculator uses a common Widmark-style estimate. In simplified form:
- A = total alcohol consumed in fluid ounces of ethanol (standard drinks × 0.6)
- W = body weight in pounds
- r = alcohol distribution ratio (commonly 0.73 male, 0.66 female)
- H = hours since drinking began
The result is capped at a minimum of 0.00, since BAC cannot go below zero.
How to Use the Calculator Correctly
1) Enter realistic numbers
Use your current body weight, estimate standard drinks honestly, and include total elapsed hours since your first drink—not just your last drink.
2) Know what counts as one standard drink
- 12 oz beer at ~5% ABV
- 5 oz wine at ~12% ABV
- 1.5 oz distilled spirits at ~40% ABV
Large pours, craft cocktails, and high-ABV beverages may equal more than one standard drink.
3) Recalculate as time passes
BAC changes over time. If your plans change, recalculate with updated hours and drink count.
BAC Levels and Typical Effects
- 0.00–0.019%: Subtle effects, little visible impairment
- 0.02–0.049%: Relaxation, mild judgment changes
- 0.05–0.079%: Noticeable impairment in coordination and reaction time
- 0.08–0.149%: Significant impairment; often above legal driving limits
- 0.15%+: Severe impairment, high safety risk
These ranges are general. People can experience different effects at the same BAC.
Practical Safety Guidance
- Do not drive after drinking—use rideshare, taxi, public transit, or a sober driver.
- Drink water between alcoholic beverages.
- Eat before and while drinking.
- Avoid drinking games and rapid consumption.
- Watch friends for warning signs of alcohol poisoning.
Limits of Any BAC Estimator
No online BAC calculator can account for all variables. Medication interactions, sleep deprivation, health conditions, genetics, and meal timing can all change real-world outcomes. Breathalyzer or blood testing is needed for direct measurement.
If someone is confused, vomiting repeatedly, has slow or irregular breathing, or is difficult to wake, treat it as an emergency and seek immediate medical help.
Frequently Asked Questions
Can coffee, cold showers, or exercise sober me up faster?
No. Only time lowers BAC meaningfully. Caffeine may make you feel more alert without reducing impairment.
How long does it take to reach zero BAC?
A rough rule is that BAC decreases by about 0.015 per hour. This calculator estimates the time needed, but your actual rate can vary.
Is this calculator valid for legal decisions?
No. It is for education only. Never use a calculator as permission to drive.