Widmark Formula: The Science of BAC

Understand the math behind Blood Alcohol Concentration estimation.

Interactive Example: Showing BAC for a 80kg male after 3 beers.

Your Variables

x

Assumes ~( 13-20g ) ethanol per drink.

Your Results

Your Alter Ego

The Philosopher 🤔

Tonight's State: Ideas become deep (or at least feel deep)

You start discussing life, the universe, and why pizza tastes better at night.

Typical behavior: deep conversations, overthinking simple topics

0.99‰

Theoretical Peak BAC

If all alcohol was consumed instantly.

0.69‰

End of Drinking BAC

Concentration when you took your last sip.

0.54‰

Current Blood Alcohol Concentration

Your estimated concentration right now.

BAC Projection

Metabolism Rate: -0.15‰ / h

📱 Phone Risk Indicator

🤔CAUTION
010038

You've opened your contacts list at least twice. For research purposes, obviously.

How likely are you to ruin a relationship right now?

Recovery Blueprint

  • Your body is still processing alcohol. Avoid driving or intense exercise.

Universal Recommendations

Electrolyte drink
Light carbohydrates
Gentle walk
Avoid more alcohol

Hangover Forecast

Your Alter Ego

The Philosopher 🤔

Theoretical Peak BAC

0.54‰

Hangover Risk

51%

Share Your Results

Challenge your friends or just let them know you might need a quiet morning tomorrow.

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Methodology

Calculations are based on the standard Widmark formula: BAC = (Total Alcohol Grams / (Weight × r)) × 0.1 - (0.015 × Hours Since Last Drink) where r depends on gender, combined with a weighted penalty model factoring in dehydration, sleep deficit, and drinking speed to estimate subjective hangover severity. Example: A 75kg male drinking two 500ml beers (5% ABV = 40g alcohol) hits ~0.80‰. Factoring in metabolism, it drops to ~0.50‰ after 2 hours.

Methodology

The Widmark formula is the gold standard for estimating Blood Alcohol Concentration (BAC). Developed by Swedish physician Erik M.P. Widmark in 1932, it remains the foundation for forensic toxicology globally.

The Mathematical Foundation

The core calculation follows: BAC = [Alcohol (g) / (Body Weight (g) × r)] × 100. Where 'r' is the distribution ratio representing the body water percentage.

BAC = (A / (W * r)) * 100

Why Gender and Weight Matter

Alcohol is water-soluble. Since muscle contains more water than fat, individuals with higher muscle mass or body water percentages (typically males) distribute alcohol across a larger volume, resulting in a lower BAC for the same amount consumed.

Beyond Simple Calculators

Most online tools assume 'instant consumption'. Our engineering-first approach factors in the absorption constant and elimination rate to map your BAC over a realistic timeline.

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