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Blood Alcohol Estimator

Quick BAC estimate using US standard drinks (14 g pure alcohol per drink), body weight and time — for a fast read on your level.

How to use

Pick sex and unit, enter your body weight, the number of standard drinks you've had and the hours since your first drink. One US standard drink = 14 g pure alcohol (≈ 12 oz beer at 5%, 5 oz wine at 12%, or 1.5 oz spirits at 40%).

1 standard drink = 14 g pure alcohol

BAC range and effect

BAC (%)Effect
0.00No impairment
0.01–0.029Feeling of warmth, slight disinhibition
0.03–0.079Reduced reaction time, elevated mood
0.08–0.149Notably slowed reaction, coordination loss — US driving limit
0.15–0.299Slurred speech, blurred vision, severe balance issues
> 0.30Impaired consciousness, vomiting, life-threatening

How it works

This estimator uses US standard drinks (14 g pure alcohol) and the Widmark formula. BAC (%) = (drinks × 14 g) / (weight × r) × 0.1 − 0.015 × hours, where r = 0.68 (male) or 0.55 (female). Elimination is approximately 0.015% per hour. Individual values can shift ±20–30% — stomach contents, liver health, medications and genetics all matter.

This estimate is no substitute for a breath or blood test. If you've been drinking: do not drive.

Frequently Asked Questions

What is a standard drink?+
A US standard drink contains 14 g of pure alcohol. That's roughly 12 oz of beer (5%), 5 oz of wine (12%) or 1.5 oz of spirits (40%). UK units are smaller (8 g) — this calculator uses the US convention.
What's the difference between BAC and promille?+
BAC in % (US) and promille (Europe) measure the same thing in different units. 0.08% BAC = 0.8‰. The result panel shows both side by side.
How fast does the body process alcohol?+
On average about 0.015% BAC per hour (≈ 0.15‰). The rate is roughly constant and cannot be sped up by coffee, water or exercise — only time.
What are the driving limits?+
US: 0.08% BAC in most states (0.04% for commercial drivers, 0.00% under 21). Germany: 0.05% / 0.5‰ (0.03% with signs of impairment, 0.00% for new drivers). Most EU countries: 0.02–0.05%.
Why is the estimate imprecise?+
Stomach contents, liver function, medications, hormonal cycle and genetics all shift real BAC. Women on average have less body water. When in doubt, assume the more conservative reading.
How is this different from the Blood Alcohol Calculator?+
The full Blood Alcohol Calculator takes individual drinks (volume × ABV) — precise but slower. This estimator uses standard drinks — faster but less fine-grained. Both use the Widmark formula.

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Background

Blood Alcohol Estimator: Standard Drinks, BAC and Driving Limits

8 min