Health

Blood Alcohol Calculator

Estimate BAC by weight and drink total, then see how the estimate fades over time.

by weightover timeestimate onlydrink countabvbac estimate

Result // Widmark estimate

Blood alcohol snapshot

Estimate only

Current BAC

0.040%

Computed at the selected elapsed time.

Time to 0.00%

2.7 h

Clear around hour 4.7 since drinking started.

Pure alcohol

1.8 oz

42.0 g in the drink total.

Estimate only

This is a rough estimate. It does not replace legal, medical, or safety judgment.

Hourly timeline

The estimate steps forward in one-hour increments and ends on the first zero row.

Clear around 4.7 h

PointEstimated BAC
Now0.040%
+1h0.025%
+2h0.010%
Clear0.000%

Need a change for Blood Alcohol Calculator?

About this calculator

Method, formulas, and limits.

What this does

Estimates blood alcohol content (BAC) based on your body weight, the number and type of drinks consumed, the alcohol percentage of each drink, and the time elapsed since you started drinking. It also shows how your estimated BAC declines over time as your body metabolizes alcohol.

Who it is for

Anyone looking for a general reference on how alcohol consumption affects BAC levels. Commonly used as an educational tool to understand the relationship between drinking and estimated BAC, not for legal or medical decisions.

How it works

The calculator uses a Widmark-style formula that divides total alcohol consumed by your estimated body water volume (based on weight and sex), then subtracts an average metabolic elimination rate multiplied by elapsed hours. The result is a rough BAC estimate that trends downward over time.

Limitations

This is an estimate only. Actual BAC varies significantly based on metabolism, food intake, medications, hydration, health conditions, and many individual factors. It should never be used to determine fitness to drive or for any legal or medical purpose.

Key calculations

Total Alcohol Consumed
Multiply each drink's volume by its ABV to get grams of alcohol. totalAlcohol = Σ (volume × abv × 0.789), where 0.789 converts milliliters of ethanol to grams.
Widmark BAC Estimate
Divide total alcohol by body water volume estimated from weight and sex. bac = totalAlcohol / (weight × distributionRatio × 10), then subtract metabolism.
BAC Over Time
Subtract the metabolized amount based on hours elapsed since drinking started. currentBAC = initialBAC − (eliminationRate × hoursElapsed). The typical elimination rate is 0.015 BAC per hour.

Reference ranges

Mild Impairment
0.02–0.05% BAC. Some loss of judgment and relaxation. Below the legal limit in all US states.
Legal Limit Boundary
0.05–0.08% BAC. Increased impairment. 0.08% is the standard legal driving limit in most US states.
Significant Impairment
0.08–0.15% BAC. Poor coordination, slowed reaction time, and reduced judgment. Legal consequences for driving.
Severe Intoxication
0.15% and above. High risk of blackout, vomiting, and alcohol poisoning. Emergency medical attention may be needed.

How to use it

  1. 1.Enter your body weightInput your weight in pounds or kilograms using the unit toggle. The calculator uses this to estimate your body water volume.
  2. 2.Select your sexChoose male or female. The Widmark formula uses different distribution ratios for each sex, which affects the BAC estimate.
  3. 3.Add drinksEnter the number of drinks, the volume per drink, and the alcohol by volume (ABV) percentage. You can add multiple drink types to reflect what you actually consumed.
  4. 4.Set the elapsed timeEnter how many hours have passed since you started drinking. The calculator subtracts the metabolized alcohol to estimate your current BAC.
  5. 5.Review the estimateThe calculator shows your estimated BAC and a graph of how it declines over the next several hours as your body metabolizes the alcohol.
  6. 6.Understand the limitationsThis is a rough educational estimate. Never use it to decide if you are safe to drive or for any legal or medical purpose.

The calculator uses a Widmark-style formula that estimates your body water volume based on weight and sex, divides the total grams of alcohol consumed by that volume, then subtracts an average metabolic elimination rate multiplied by the hours elapsed since you started drinking. The result is a rough BAC percentage that trends downward over time.

Real BAC varies significantly based on individual metabolism, how much food you have eaten, medications you are taking, your hydration level, overall health, and many other factors that this simple model cannot account for. Two people with the same weight and drink count can have very different actual BAC levels.

Yes. You can switch between imperial (pounds, fluid ounces) and metric (kilograms, milliliters) units using the toggle at the top of the calculator. All calculations adjust automatically to maintain accuracy.

No. This calculator provides a rough educational reference only and should never be used to determine fitness to drive or for any legal or medical purpose. Actual BAC depends on many individual factors that cannot be modeled here. Always err on the side of caution and arrange alternate transportation if you have been drinking.

Food consumption slows alcohol absorption significantly, so a full stomach can produce a lower peak BAC than an empty one. Liver health, medications, fatigue, and carbonation in drinks can also affect how quickly alcohol enters and leaves your system. Genetic differences in metabolism enzymes cause wide variation between individuals.

The average person metabolizes alcohol at a rate of about 0.015 BAC per hour, meaning it takes roughly one hour to eliminate one standard drink. However, this rate varies by individual, and higher BAC levels take proportionally longer to clear. Time is the only reliable way to reduce BAC — coffee, cold showers, and exercise do not speed up metabolism.

Yes. The Widmark formula accounts for sex through different distribution ratios (0.68 for men and 0.55 for women on average), which reflect differences in typical body water percentage. Food intake is not modeled here but can significantly reduce peak BAC by slowing alcohol absorption into the bloodstream.

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