Blood Alcohol Content (BAC) Calculator
Estimate your Blood Alcohol Content based on drinks consumed, body weight, and time elapsed using the scientifically-validated Widmark formula.
Important Disclaimer
This calculator provides estimates only. Many factors affect actual BAC. Never drink and drive. If you've been drinking, use a designated driver, rideshare, or taxi.
Understanding Blood Alcohol Content (BAC)
What is BAC?
Blood Alcohol Content (BAC) is a measure of the amount of alcohol in your bloodstream, expressed as a percentage. For example, a BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood. BAC is the standard measurement used by law enforcement to determine legal intoxication and is directly correlated with impairment levels.
How is BAC Measured?
BAC can be measured through breath, blood, or urine tests. Breathalyzers are most common for roadside testing because they're non-invasive and provide immediate results. Blood tests are the most accurate but require medical personnel. This calculator uses the Widmark formula, developed in the 1930s and still widely used in forensic science, to estimate BAC based on consumption, body weight, gender, and time elapsed.
Factors Affecting BAC
Physical Factors
- • Body weight and composition
- • Gender (water content differences)
- • Age and metabolism rate
- • Liver health and enzyme production
Environmental Factors
- • Food consumption (timing & amount)
- • Drinking speed and pattern
- • Type of alcohol consumed
- • Medications and health conditions
Alcohol Metabolism
The human liver metabolizes alcohol at a relatively constant rate of about 0.015% BAC per hour, equivalent to roughly one standard drink per hour. This rate cannot be significantly increased through any means - not coffee, cold showers, exercise, or food. The enzyme alcohol dehydrogenase in the liver breaks down alcohol into acetaldehyde, then into acetic acid, which is eventually converted to carbon dioxide and water. This process takes time and cannot be rushed.
Safety Tips
- • Never drive after drinking - impairment starts well before 0.08%
- • Plan transportation in advance (designated driver, rideshare, taxi)
- • Eat before and while drinking to slow alcohol absorption
- • Pace yourself - one drink per hour maximum
- • Stay hydrated with water between alcoholic drinks
- • Know your limits and respect them
- • Watch for signs of alcohol poisoning in others