Free Blood Alcohol Calculator (BAC) – Estimate Your Blood Alcohol Content
A blood alcohol content (BAC) calculator is a tool that estimates the concentration of alcohol in your bloodstream based on several factors. Understanding your BAC is important for making responsible decisions about driving and recognizing the effects of alcohol on your body. Our calculator uses the Widmark formula, the most widely accepted scientific method for estimating BAC.
The Widmark formula calculates BAC as: (alcohol consumed in grams) / (body weight in grams x Widmark factor) x 100, minus the metabolism rate (0.015% per hour) multiplied by time since the first drink. The Widmark factor accounts for differences in body water content: 0.68 for males and 0.55 for females, reflecting that women typically have a lower proportion of body water and therefore reach higher BAC levels from the same amount of alcohol.
Each "standard drink" contains approximately 14 grams of pure alcohol — this is equivalent to a 355ml beer at 5% ABV, a 150ml glass of wine at 12% ABV, or a 45ml shot of spirits at 40% ABV. The body metabolizes alcohol at an average rate of about 0.015% BAC per hour, though this varies by individual. Factors such as food intake, liver health, medications, genetics, and hydration all affect actual alcohol processing.
The legal driving limit in most countries is a BAC of 0.08%, though many jurisdictions have lower limits (0.05% in much of Europe and Australia, and 0.00% for commercial drivers and minors in many places). Even below the legal limit, any amount of alcohol impairs reaction time, judgment, and coordination. This calculator is for educational purposes only — never rely on any calculator to decide whether you are safe to drive. When in doubt, always arrange alternative transportation.