Overview
This blood alcohol concentration calculator provides a theoretical BAC estimate based on drink consumption and personal inputs. It uses a version of the Widmark formula and accounts for elapsed time through a standard linear alcohol-elimination rate.
The result is an approximation rather than a direct measurement. Individual physiology and drinking conditions can cause actual blood alcohol concentration to differ from the calculated value.
Key Inputs and Features
The calculator supports common drink types as well as custom servings:
- Beer based on a 12-ounce serving at 5% alcohol
- Wine based on a 5-ounce serving at 12% alcohol
- Liquor based on a 1.5-ounce serving at 40% alcohol
- Custom drinks entered by volume and alcohol percentage
- Weight entered in pounds or kilograms
- Time measured from the first drink
It displays an estimated BAC percentage and an accompanying impairment range.
How to Use the Calculator
Select sex, enter body weight, and provide the number of hours since the first drink. Then add the consumed drinks using the standard serving options or the custom volume and alcohol fields.
The calculation converts consumed alcohol into grams, adjusts for body weight and a sex-based distribution coefficient, and subtracts estimated metabolic elimination over time. The stated elimination baseline is approximately 0.015% BAC per hour.
Factors That Affect an Estimate
The Widmark calculation offers a standardized baseline, but it cannot capture every biological variable. Food can slow movement of alcohol from the stomach to the small intestine, while body composition affects how alcohol distributes through body water. Dehydration may also raise alcohol concentration relative to available fluid volume.
Standard drink definitions vary by country, so serving size and alcohol content should be entered carefully. Carbonation may accelerate gastric emptying, while caffeine, cold showers, and exercise may increase alertness without speeding liver metabolism.
Important Limitations
A calculated BAC should not be treated as a legal, medical, or driving-safety determination. The tool produces a theoretical estimate and cannot confirm sobriety or account precisely for personal metabolism, absorption, medications, health conditions, or measurement error.
Direct testing is different from formula-based estimation. Decisions about driving or other safety-sensitive activities should not rely on a calculator result.