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🚨 For educational purposes only. Never drink and drive. This tool does not determine whether you are safe to drive.

🍺 Blood Alcohol Calculator

Estimate your Blood Alcohol Concentration (BAC) using the Widmark formula. Enter your gender, weight, number of drinks consumed, and elapsed time.

Widmark factor: Male 0.68, Female 0.55

kg lbs

1 standard drink = 14g pure alcohol (US)

BAC Levels & Effects

BAC Level Category Typical Effects
< 0.02% Minimal No significant impairment
0.02–0.05% Mild Relaxation, mild euphoria, slight impairment
0.05–0.08% Impaired Reduced coordination, judgment affected
0.08%+ Legally drunk Driving illegal in most countries
0.15%+ Severely impaired Major loss of coordination, vomiting possible
0.30%+ Dangerous Loss of consciousness, risk of death

Widmark Formula

Alcohol (g) = drinks × 14
BAC = Alcohol(g) / (weight(g) × r) × 100
r = 0.68 (male) or 0.55 (female)
BAC adjusted = BAC − (0.015 × hours)
Minimum 0 (body metabolises ~0.015% per hour)

How to Use This Calculator

  1. 1
    Select Gender
    The Widmark r-factor differs by gender due to differences in body water content.
  2. 2
    Enter Your Weight
    Toggle between kg and lbs. Heavier people generally reach a lower BAC from the same number of drinks.
  3. 3
    Count Standard Drinks
    One US standard drink = 14g pure alcohol (12oz 5% beer, 5oz 12% wine, or 1.5oz 40% spirits).
  4. 4
    Enter Time Elapsed
    Your body metabolises about 0.015% BAC per hour. The longer you wait, the lower your BAC.

Real-World Example

Male, 80 kg, 3 standard drinks, 1.5 hours elapsed:

Alcohol = 3 × 14 = 42g
BAC raw = 42 / (80,000 × 0.68) × 100 = 0.0772%
Metabolism = 0.015 × 1.5 = 0.0225%
BAC adjusted = 0.0772 − 0.0225 = 0.055%
Hours to sober = 0.055 / 0.015 ≈ 3.7 hours

Important Disclaimer

This is an estimate only. Many factors affect BAC including food intake, medication, individual metabolism, tolerance, and hydration. Do not use this calculator to determine if you are safe to drive. If you have consumed alcohol, use a ride service or a designated driver.

Frequently Asked Questions

The Widmark formula estimates BAC: divide the grams of alcohol consumed by (body weight in grams × the Widmark r-factor: 0.68 for males, 0.55 for females), then multiply by 100. The body eliminates approximately 0.015% BAC per hour, which is subtracted from the raw result.

In the United States, one standard drink contains 14 grams of pure alcohol. This equals roughly 355ml (12oz) of 5% beer, 148ml (5oz) of 12% wine, or 44ml (1.5oz) of 40% distilled spirits. Note that craft beers and large wine pours can contain significantly more.

On average, the body metabolises alcohol at roughly 0.015% BAC per hour (about one standard drink per hour). This rate varies by individual and cannot be meaningfully accelerated by coffee, food, or cold showers — only time reduces BAC.

Most countries set the legal driving limit at 0.05% or 0.08% BAC. The US, Canada, UK, and Australia use 0.05–0.08%. Many European countries use 0.05%. Some countries have zero-tolerance (0.00%) laws. Always check your local laws as limits vary.

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