Blood Alcohol Calculator — BAC Calculator Online

Estimate your blood alcohol content — free, instant & educational

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Disclaimer: This calculator is for informational and educational purposes only. It provides rough estimates and cannot account for all individual factors. Never drink and drive. If in doubt, do not drive.

Estimate Your Blood Alcohol Content

Estimated BAC
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Last updated: Mar 23, 2026

Our free Blood Alcohol Calculator uses the Widmark formula to estimate your BAC (Blood Alcohol Content) based on the number of drinks, your body weight, biological sex, and time elapsed. This tool is for educational purposes only — never drink and drive.

What is Blood Alcohol Content (BAC)?

Blood Alcohol Content (BAC), also known as Blood Alcohol Concentration, measures the percentage of alcohol in your bloodstream. A BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood.

BAC is the standard measurement used by law enforcement to determine legal intoxication. In most US states, a BAC of 0.08% is the legal limit for drivers over 21. Many European countries use lower limits of 0.05% or even 0.00%.

Your BAC depends on several factors: how much you drank, your body weight, biological sex, how quickly you drank, and how much time has passed since your last drink.

The Widmark Formula

Our calculator uses the Widmark formula, the most widely accepted method for estimating BAC:

BAC = (Alcohol in grams / (Body weight in grams × r)) × 100 − (0.015 × hours) Where r = 0.68 (male) or 0.55 (female)

The factor r (Widmark factor) accounts for differences in body water content between biological sexes. The 0.015 per hour represents the average rate at which the liver metabolizes alcohol. Learn more on our alcohol metabolism page.

BAC Levels and Their Effects

1

0.01 – 0.03% — Minimal Effects

Slight mood elevation. No apparent impairment. Relaxation.

2

0.03 – 0.06% — Mild Impairment

Lowered inhibitions, mild euphoria. Slight impairment of judgment and memory.

3

0.06 – 0.10% — Increased Impairment

Reduced coordination, reaction time, and peripheral vision. Judgment significantly affected. Legally impaired in most jurisdictions.

4

0.10 – 0.20% — Severe Impairment

Poor muscle control, slurred speech, blurred vision. Significant risk of injury. Do not drive under any circumstances.

5

0.20%+ — Dangerous

Risk of blackout, vomiting, loss of consciousness. Above 0.30% is life-threatening. Seek medical help.

Factors That Affect Your BAC

1
Body Weight: Heavier individuals generally have lower BAC for the same amount of alcohol, because alcohol is distributed across a larger volume of body water.
2
Biological Sex: Females typically have a higher BAC than males after the same number of drinks, due to differences in body water percentage and metabolism.
3
Rate of Consumption: Drinking quickly raises BAC faster than spacing drinks out over time, because the liver can only metabolize about one standard drink per hour.
4
Food Intake: Drinking on an empty stomach causes alcohol to be absorbed faster, leading to a higher peak BAC. Food slows absorption but doesn't prevent intoxication.
5
Alcohol Content: Higher ABV drinks deliver more alcohol per serving. A standard drink contains about 14 grams of pure alcohol regardless of beverage type.

Frequently Asked Questions

How long does it take for BAC to reach zero?
On average, the body metabolizes alcohol at a rate of about 0.015% BAC per hour. So if your BAC is 0.08%, it would take roughly 5.3 hours to reach 0.00%. This rate varies between individuals.
Can coffee, cold showers, or food lower my BAC faster?
No. Only time reduces BAC. Coffee may make you feel more alert, but it does not speed up alcohol metabolism. Food can slow absorption of new alcohol but will not reduce alcohol already in your bloodstream.
How accurate is the Widmark formula?
The Widmark formula provides a reasonable estimate but cannot account for individual variations in metabolism, food intake, medications, liver health, and other factors. It should never be used as the sole basis for deciding whether to drive.
What is the legal BAC limit for driving?
It varies by country and jurisdiction. In the US, the legal limit is 0.08% for drivers over 21. In many European countries, it's 0.05%. Some countries have a zero-tolerance policy (0.00%). See our DUI limits page for a full breakdown.
What is a standard drink?
In the US, a standard drink contains about 14 grams of pure alcohol. This is equivalent to 12 oz of beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV). Learn more on our standard drinks page.
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Blood-Alcohol-Calculator.com Editorial Team
Created and reviewed by our health & science editorial team. All formulas and information are regularly checked for accuracy.