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Blood Alcohol Content (BAC) Calculator

Estimate your BAC using the Widmark formula. This is a rough estimate only and must NOT be used to decide whether it is safe to drive.

kg

1 standard drink = 14g alcohol (12 oz beer, 5 oz wine, 1.5 oz spirits)

Estimated Blood Alcohol Content

0.05%

Slightly Impaired

Some loss of coordination; mild euphoria. This is a rough estimate based on the Widmark formula and individual factors (metabolism, food, medication, tolerance) that affect actual BAC. Do NOT use this to decide if you can drive. When in doubt, use a designated driver or taxi.

Alcohol Consumed42.00g
Body Weight (kg)75.00kg
Est. Time to Sober3.49hrs

What is the Blood Alcohol Content (BAC) Calculator?

Blood Alcohol Content (BAC), also called Blood Alcohol Level (BAL), is the percentage of alcohol in your bloodstream. It's measured as grams of ethanol per 100 milliliters of blood. The Widmark formula—used by forensic analysts, emergency rooms, and researchers—estimates BAC by dividing the grams of alcohol consumed by body weight adjusted for water content (the distribution ratio), then subtracting metabolism (approximately 0.015% per hour). Unlike a breathalyzer or blood test, this calculator cannot measure your actual BAC, but it gives a reasonable estimate for educational purposes.

How it works

The calculator collects your biological sex, body weight, number of standard drinks consumed, and hours elapsed since your first drink. It then applies the Widmark formula: BAC% = (Alcohol Grams ÷ (Body Weight in grams × Distribution Ratio)) × 100 − (0.015 × Hours). The distribution ratio accounts for the fact that women have less total body water than men (55% for females vs. 68% for males), so alcohol reaches a higher concentration in female bodies. The calculator subtracts 0.015% per hour to account for your liver's metabolism, then floors the result at 0% so it never goes negative.

BAC% = (Alcohol Grams ÷ (Body Weight in grams × Distribution Ratio)) × 100 − (0.015 × Hours)

Alcohol Grams = number of drinks × 14g per standard drink. Body Weight in grams = weight in kg × 1,000. Distribution Ratio = 0.68 for males, 0.55 for females (reflects water content in body). Metabolism = 0.015% per hour (liver clears ~1 drink per hour). Each variable affects the final BAC: more drinks increase it, higher body weight decreases it, and longer time decreases it due to metabolism.

Examples

InputResultNotes
Male, 75 kg, 3 standard drinks, 2 hours elapsedBAC ≈ 0.06% (Slightly Impaired); loss of coordination, mild euphoriaTypical scenario: 3 beers over 2 hours. Reaction time and judgment begin to decline.
Female, 60 kg, 2 standard drinks, 1 hour elapsedBAC ≈ 0.08% (Moderately Impaired); slowed reaction, reduced judgmentLower distribution ratio (0.55 vs. 0.68) means women reach higher BAC at the same weight and drink count. This reaches legal driving limit in many jurisdictions.
Male, 90 kg, 4 standard drinks, 3 hours elapsedBAC ≈ 0.07% (Moderately Impaired); impaired coordination and speechHeavier drinker; higher body weight buffers the effect, but metabolism has had time to work.

How to use the Blood Alcohol Content (BAC) Calculator

  1. Select your biological sex (determines water content ratio for metabolism).
  2. Enter your body weight in kilograms or pounds (use the toggle to switch units).
  3. Count the number of standard drinks consumed (1 standard = 12 oz beer, 5 oz wine, 1.5 oz spirits).
  4. Enter hours elapsed since your first drink (liver metabolizes ~0.015% per hour).
  5. View your estimated BAC, impairment level, and time to sobriety.
  6. Remember: this is a rough estimate; actual BAC depends on food, metabolism, medications, and tolerance.

Benefits

  • Understand how alcohol affects your body based on your personal factors (sex, weight, drink count).
  • Learn the relationship between drinks consumed and impairment level—useful for awareness.
  • See how time and metabolism gradually reduce BAC; helps you understand why 'sleeping it off' works.
  • Educational tool for harm reduction: recognize impairment thresholds before they catch you off guard.
  • Instant, private calculation—no sign-up; educate yourself anytime, anywhere.
  • Helps reinforce that safe driving requires BAC below 0.08% (or 0.00% in many regions); when in doubt, don't drive.

Tips & common mistakes

Common mistakes

  • Thinking all bodies process alcohol at the same rate; weight and sex matter significantly, and individual metabolism varies widely.
  • Forgetting that food, medication (especially painkillers), and sleep deprivation affect how quickly alcohol is absorbed.
  • Using this calculator to decide it's safe to drive; even at 0.07% BAC, reaction time and judgment are impaired.
  • Confusing BAC with intoxication level; some people feel drunk earlier, others suppress signs—tolerance is not the same as safety.

Tips

  • Eat food before or while drinking; it slows alcohol absorption and gives your liver more time to work.
  • Alternate alcoholic drinks with water; hydration reduces perceived impairment and hangover severity.
  • Track your actual drinks, not approximations; 'a couple of drinks' is vague—count standard drink sizes.
  • Plan your transport before drinking; designated drivers, taxis, and rideshare apps are cheaper than the cost of impaired driving.
  • If you reach BAC 0.10% or higher, stay somewhere safe and sober up; never drive or operate machinery.

Frequently asked questions

What is a standard drink?

A standard drink contains 14 grams of ethanol (pure alcohol). This equals 12 ounces of 5% beer, 5 ounces of 12% wine, or 1.5 ounces of 40% spirits (liquor). Craft beers, strong wines, and mixed drinks often exceed this amount, so check labels or ask bartenders for actual volume and ABV.

Why is the distribution ratio different for men and women?

Women have less total body water than men (55% vs. 68% on average). Since alcohol dissolves in water, the same drink raises BAC higher in a woman's body. This is why a woman and man of the same weight who drink the same amount will have different BACs. Individual hydration status also matters.

Is this calculator accurate enough to use for legal or medical decisions?

No. This is an educational estimate only. Actual BAC varies based on food, medication, liver function, stomach lining, hydration, hormonal cycle, and metabolism—none of which this calculator measures. Only a breath test, blood test, or saliva test can measure your real BAC. Never use this calculator to decide if it's safe to drive.

How fast does my body metabolize alcohol?

On average, your liver clears about 0.015% BAC per hour (roughly one standard drink per hour). However, metabolism varies by individual: liver disease, medication, age, and genetics affect this rate. Some people metabolize alcohol 25% faster or slower than average, so this is an approximation.

What BAC am I at when I start to feel impaired?

Feeling drunk is highly individual and affected by tolerance, food, medication, and fatigue. However, at 0.08% BAC (the legal driving limit in many places), most people show measurable impairment in reaction time and judgment, even if they feel fine. Below 0.05%, most people report no noticeable effect, though impairment may still exist. Never rely on 'feeling okay' to drive.

Can I speed up how fast my body clears alcohol?

No. Your liver metabolizes alcohol at a fixed rate (~0.015% per hour). Coffee, cold showers, or exercise do not speed this up. The only thing that clears alcohol from your system is time. Eating and hydrating before or during drinking may slow absorption, but they don't accelerate metabolism.

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FreeToolz Editorial Team · Last reviewed July 2026

Reviewed for accuracy. Results are estimates for general information and are not professional (medical, financial or legal) advice.