BAC Calculator - Blood Alcohol Content Estimator Free BAC Calculator
Estimate your blood alcohol content (BAC) using the Widmark formula. Enter the number of drinks, your weight, gender, and hours since your first drink. For educational purposes only.
Drink Details
BAC Results
Disclaimer: This calculator provides estimates for educational purposes only. Actual BAC varies based on many factors including food intake, metabolism, medications, and tolerance. Never drink and drive.
BAC Calculator - Guide
What is Blood Alcohol Content (BAC)?
Blood Alcohol Content (BAC) is the percentage of alcohol present in your bloodstream. It is the standard measure used to assess intoxication levels. A BAC of 0.08% means 0.08 grams of alcohol per 100 millilitres of blood.
This calculator uses the Widmark formula, the most widely used method for estimating BAC based on the amount of alcohol consumed, body weight, gender, and time elapsed.
The Widmark Formula
BAC = (A / (W × r)) × 100 − (T × 0.015)
Where:
- A = Alcohol consumed in grams (1 standard drink = 14g)
- W = Body weight in grams
- r = Gender constant (Male: 0.68, Female: 0.55)
- T = Time since first drink in hours
- 0.015 = Average metabolic elimination rate per hour
BAC Impairment Levels
- 0.00–0.02%: Sober — No apparent effects, normal behaviour
- 0.02–0.05%: Minimal — Mild euphoria, slight relaxation, some loss of inhibition
- 0.05–0.08%: Mild — Lowered alertness, impaired judgement, reduced coordination
- 0.08–0.15%: Significant — Legally impaired in most jurisdictions. Poor balance, slurred speech, impaired vision
- 0.15–0.30%: Severe — Major loss of balance, vomiting likely, significant mental impairment
- 0.30%+: Life-Threatening — Loss of consciousness, risk of alcohol poisoning, medical emergency
What is a Standard Drink?
- Beer (5% ABV): ~350 ml (12 oz) = 1 standard drink
- Wine (12% ABV): ~150 ml (5 oz) = 1 standard drink
- Spirits (40% ABV): ~45 ml (1.5 oz) = 1 standard drink
- Strong Beer (8% ABV): ~220 ml = 1 standard drink
Important Safety Information
- Never Drink and Drive: Even a small amount of alcohol impairs your ability to drive safely.
- Individual Variation: BAC is affected by food intake, hydration, medications, fatigue, and individual metabolism.
- This is an Estimate: Only a breathalyser or blood test can provide an accurate BAC reading.
- Seek Help: If someone shows signs of alcohol poisoning (unconsciousness, slow breathing, vomiting while passed out), call emergency services immediately.