Alcohol Detection Calculator

The liver processes alcohol at a fixed rate of approximately 0.015 BAC per hour (about one standard drink per hour). This means a BAC of 0.08 takes roughly 5.3 hours to reach zero. However, alcohol metabolites like ethyl glucuronide (EtG) can be detected in urine for 48–80 hours after the last drink, well beyond the point where you feel sober.

What this calculator does

A standard drink contains approximately 14 grams of pure alcohol: 12oz beer (5%), 5oz wine (12%), or 1.5oz spirits (40%). Your BAC depends on how many standard drinks you've consumed, your body weight, biological sex, food intake, and drinking speed.

How it works

EtG (ethyl glucuronide) urine tests are far more sensitive than traditional alcohol tests and can detect consumption for 48–80 hours. These tests are commonly used in court-ordered monitoring, probation, and professional licensing programs.

Factors that affect alcohol metabolism: liver health, genetic enzyme variations (ADH and ALDH), food consumption, medications, age, and overall health. Women typically metabolize alcohol more slowly due to lower body water content and different enzyme activity.

When to use this calculator

Use this calculator as a starting point for any health or fitness goal that requires a numeric benchmark. The result is an estimate, not a diagnosis — but it provides a concrete figure to track against over time.

Common mistakes

Many users apply adult health classifications to children and teenagers, which is incorrect. Paediatric norms for height, weight, BMI, and body composition are age-and-sex-specific. Use age-appropriate reference tools for anyone under 18.

Real-world scenarios

A nurse calculates a patient's health metric during a routine assessment, then uses the result alongside other clinical indicators to contextualise the finding — correctly treating the number as one data point among several rather than a standalone answer.

Formula

BAC Decline Rate

BAC = (Drinks × 0.06) / (Weight in kg × 0.7) − (0.015 × Hours)

BAC starts declining once the liver begins processing. The fixed elimination rate of ~0.015/hour means heavier drinking requires proportionally longer to reach zero BAC.

Worked example

A 75kg male drinks 5 beers over 3 hours.

  1. Estimated peak BAC: (5 × 0.06) / (75 × 0.7) = 0.057
  2. Minus 3 hours of metabolism: 0.057 − (0.015 × 3) = 0.012
  3. Time to reach 0.00 BAC: approximately 0.8 more hours
  4. EtG urine detection: 48–80 hours after last drink
  5. Blood alcohol: undetectable after ~5 hours total

Result: BAC returns to zero approximately 4–5 hours after the last drink. However, EtG urine tests can detect this consumption for 2–3 days. Full hangover recovery: 24–48 hours.

Frequently asked questions

How long does alcohol stay in urine?

Traditional tests: 12–48 hours. EtG tests: 48–80 hours for moderate drinking. Heavy drinking can be detected via EtG for up to 5 days.

How fast does your body process alcohol?

The liver processes approximately one standard drink per hour (0.015 BAC per hour). This rate is relatively fixed — coffee, cold showers, and exercise do not speed it up.

Can you fail a breathalyzer the morning after?

Yes. If you had 8+ drinks, your BAC may still be above 0.08 the next morning. A BAC of 0.12 takes 8 hours to reach zero. Many DUI arrests occur the morning after heavy drinking.

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