Blood Alcohol Content (BAC) Calculator

This tool gives an educational estimate of blood alcohol content from the number of standard drinks, your weight, sex, and time elapsed, using the Widmark formula. It is not a measurement and must never be used to decide whether it is safe to drive.

Worked Example

Sample input: Standard drinks consumed: 2, Body weight (kg): 70, Sex (1 = male, 0 = female): 1, Hours since first drink: 1

Estimated BAC: 0.044 (Below US legal driving limit (0.08))

After 2 standard drinks over 1 hour(s) at 70 kg, your estimated BAC is about 0.044% (Widmark formula). This is an educational estimate only — never use it to decide whether to drive.

Frequently Asked Questions

How is BAC estimated?

We use the Widmark formula. Grams of alcohol (14 g per US standard drink, per NIAAA) are divided by body water (weight times a distribution ratio of 0.68 for men or 0.55 for women), then we subtract 0.015 percent per hour for elimination.

Is this accurate enough to decide whether to drive?

No. Absolutely not. Real BAC varies widely with food, metabolism, medications, and hydration, and this estimate can be off in either direction. Never use it to judge whether you are safe to drive. If you drink, do not drive.

What is one standard drink?

In the US a standard drink contains about 14 grams of pure alcohol, roughly equal to a 12-ounce regular beer, a 5-ounce glass of wine, or a 1.5-ounce shot of spirits.

How long does alcohol take to leave the body?

The body eliminates alcohol at roughly 0.015 percent BAC per hour, and this rate cannot be sped up by coffee, food, or a cold shower. Only time lowers BAC.

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