Free BAC Calculator
Estimate your Blood Alcohol Content (BAC) with our free calculator. Uses the Widmark formula based on gender, weight, drinks consumed, and time elapsed.
Estimated BAC
0.046%
✓ Below legal limit (0.08%)
Time Until Sober
3h 3m
Standard Drinks
3
Beer (12 oz, 5%)
⚠ For educational purposes only. This is an estimate and should NOT be used to determine if you are safe to drive. Many factors affect actual BAC. When in doubt, don't drive.
Formula
BAC = (Alcohol in grams / (Body weight in grams × r)) × 100 − (hours × 0.015) — where r = 0.68 (male) or 0.55 (female)Understanding Blood Alcohol Content
Blood Alcohol Content (BAC) measures 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. This metric is used worldwide as the standard measure of intoxication for legal and medical purposes.
Our calculator uses the Widmark formula, developed by Swedish professor Erik Widmark in the 1930s. It estimates BAC based on the amount of alcohol consumed, body weight, a gender-specific distribution ratio, and the time elapsed since drinking. While useful for estimation, actual BAC depends on many individual factors.
BAC Levels and Their Effects
- 0.02-0.03%: Slight mood elevation, mild relaxation. Most people feel minimal effects.
- 0.04-0.06%: Lowered inhibitions, warmth, relaxation. Minor impairment of reasoning and memory.
- 0.07-0.09%: Mild impairment of balance, speech, vision, reaction time, and hearing. Judgment is reduced.
- 0.10-0.12%: Significant impairment of motor coordination. Slurred speech, poor judgment, reduced reaction time.
- 0.13-0.15%: Major loss of balance. Blurred vision, anxiety, restlessness. Vomiting may occur.
- Above 0.15%: Serious impairment. Risk of blackout, loss of consciousness, and alcohol poisoning increases rapidly.
Factors That Affect BAC
Many variables influence how alcohol affects your body beyond what any formula can capture:
- Food intake — eating before or while drinking slows alcohol absorption significantly
- Drink speed — consuming drinks quickly raises BAC faster than spacing them out
- Medications — many medications interact with alcohol and can amplify its effects
- Fatigue and stress — being tired or stressed can increase perceived impairment
- Tolerance — regular drinkers may feel less impaired at the same BAC, but the actual impairment and health risks remain
Important Safety Reminder
This calculator is for educational purposes only. Never use a BAC estimate to decide whether you're safe to drive. Impairment begins at BAC levels well below the legal limit. The safest choice is always to use a designated driver, rideshare, or taxi after consuming any amount of alcohol.
Frequently Asked Questions
How accurate is this BAC calculator?
This calculator provides a rough estimate based on the Widmark formula. Actual BAC depends on many factors not accounted for here, including food intake, medications, liver health, hydration level, and individual metabolism. Never rely on a calculator to determine if you're safe to drive — when in doubt, don't drive.
What is the legal BAC limit for driving?
In most US states, the legal limit is 0.08% BAC for drivers 21 and over. For commercial drivers, it's typically 0.04%. For drivers under 21, most states have zero-tolerance laws (0.00-0.02%). Many countries have lower limits — for example, 0.05% in most of Europe and Australia. Impairment begins well below the legal limit.
How long does it take to sober up?
The body metabolizes alcohol at roughly 0.015% BAC per hour (about one standard drink per hour). This rate is relatively constant and cannot be sped up by coffee, cold showers, or exercise. If your BAC is 0.08%, it would take approximately 5.3 hours to reach 0.00%.
What counts as one standard drink?
In the US, one standard drink contains about 14 grams of pure alcohol. This equals approximately 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV). Many cocktails and craft beers contain significantly more alcohol than one standard drink.
Why does gender affect BAC?
Women generally reach higher BAC levels than men of the same weight after consuming the same amount of alcohol. This is due to differences in body water content and the Widmark 'r' factor: men have about 68% water by weight versus 55% for women. More body water means alcohol is more diluted, resulting in lower BAC.