BAC Calculator
BAC Calculator
| Metric | Value |
|---|---|
| Estimated BAC | 0.040% |
| Impairment Level | Mild Euphoria |
| Pure Alcohol Consumed | 1.80 oz |
| Standard Drinks Equivalent | 3.0 |
| Gender Constant (r) | 0.73 |
| Time to Reach 0.00% | 2.7 hrs |
| US Legal Driving Limit | Under 0.08% |
BAC vs. Legal Limits & Impairment
The dashed line marks the US/UK legal driving limit (0.08%). Your estimated BAC is shown in the first bar.
Summary Statistics
What Is a BAC Calculator?
A Blood Alcohol Content (BAC) calculator estimates the concentration of alcohol in your bloodstream after drinking, expressed as a percentage of alcohol by volume in blood. It uses the Widmark formula, developed by Swedish physiologist Erik Widmark, which factors in your body weight, sex, the amount of pure alcohol consumed, and the time elapsed since your first drink. With defaults of a 180-lb male having 3 standard beers over 2 hours, the tool estimates a BAC around 0.05% — approaching the legal driving limit in Canada and most of the EU. BAC is the metric used by law enforcement worldwide to determine legal impairment, making it critical for understanding when it is unsafe or illegal to drive.
How the Widmark Formula Works
The core formula is BAC = (A × 5.14 / (W × r)) − 0.015 × H, where A is the total ounces of pure alcohol consumed, W is body weight in pounds, r is the gender distribution ratio (0.73 for men, 0.66 for women), and H is the number of hours since the first drink. The Advanced Options let you set exact ABV and drink volume so A is computed precisely: A = drinks × (ABV ÷ 100) × volume in ounces. Because women have less body water, their lower r value produces a higher BAC for the same intake. The liver then metabolizes alcohol at a steady rate — about 0.015 BAC per hour — which is why time is the only reliable way to sober up. Dividing your current BAC by that rate gives the estimated hours until you return to 0.00%.
Impairment Levels and Legal Limits
Impairment rises steadily with BAC. At 0.02% you may feel subtle relaxation; by 0.05% coordination and judgment decline; at 0.08% — the legal limit in the US and UK — muscle coordination is clearly impaired; and beyond 0.30% there is real risk of stupor, coma, or death. Legal driving limits differ by country: 0.08% in the US and UK, but 0.05% in Canada and most EU nations, with stricter limits for commercial and underage drivers. This calculator is intended for education and awareness only. Real BAC depends on food intake, medication, genetics, hydration, and drinking speed, none of which averages can fully capture. Never rely on an estimate to decide whether to drive — if you have been drinking, arrange a ride or wait it out.
Frequently Asked Questions
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