The BAC Calculator estimates blood alcohol content from drink count, body weight, biological sex, and elapsed time using the Widmark pharmacokinetic formula. An educational reference for alcohol metabolism physiology — formula estimates cannot substitute for clinical breathalyzer measurement.
0.045
%
0.075
%
0.03
%
3
hours
56
%
0.035
%
0.045
%
0.075
%
0.03
%
3
hours
56
%
0.035
%
The Widmark equation has been used in pharmacokinetics and forensic toxicology since 1932 to estimate blood alcohol concentration from consumption parameters. The calculator for blood alcohol content applies this formula to give a rough BAC estimate based on standard drink count, body weight, biological sex, and time since drinking began — a useful educational reference for understanding the physiology of alcohol metabolism, while acknowledging that individual variation makes any formula an approximation rather than a reliable personal predictor.
Swedish physician Erik Widmark derived his formula in 1932 from empirical measurements of alcohol pharmacokinetics:
BAC = [Alcohol consumed (g) / (Body weight (g) × r)] − β × t
where r is the Widmark factor (0.68 for men, 0.55 for women — the ratio of body water in which alcohol distributes), β is the elimination rate constant (approximately 0.015–0.020 g/dL/hour), and t is hours since drinking commenced. Alcohol consumed in grams = drinks × 14 g per standard US drink. For a 70 kg male consuming 3 standard drinks over 2 hours: Alcohol = 42 g; BAC = 42/(70,000 × 0.68) − 0.015 × 2 = 0.0882 − 0.030 = 0.058 g/dL = 0.058%. Use this online calculator for any scenario.
The Widmark formula has substantial limitations that are critical to understand before relying on any BAC estimate:
The only accurate BAC measurement is breath alcohol testing (calibrated evidential breathalyzer) or blood draw with certified laboratory analysis. This calculator is for educational understanding of the pharmacokinetics, not for personal driving decisions.
BAC thresholds and their physiological effects:
The alcohol consumption calculator quantifies intake in standard drink equivalents across different beverage types.
A "standard drink" contains different amounts of pure alcohol depending on jurisdiction — a critical variable for BAC calculations:
This calculator uses the US 14 g standard. When using drinks consumed from other countries as inputs, convert to US equivalents for accurate results.
The Widmark formula, developed by Swedish pharmacologist Erik Widmark in the 1930s, is the standard method for BAC estimation:
$$BAC = \frac{A \times 5.14}{W \times r} - 0.015 \times H$$
Where: A = number of standard drinks × 0.6 (oz of alcohol per drink), W = body weight in pounds, r = Widmark factor (0.73 for males, 0.66 for females), H = hours since drinking began, and 0.015 = average alcohol metabolism rate per hour (%/hour).
The factor 5.14 converts fluid ounces of alcohol to grams per deciliter in the blood. The r factor represents the ratio of body water to total body weight — lower in females because adipose tissue contains little water. Alcohol is eliminated at approximately 0.015–0.020% BAC per hour — the average elimination rate used in this calculator is 0.015.
Time to sober is estimated as current BAC divided by the elimination rate of 0.015 per hour.
At 0.02–0.04% BAC: mild relaxation, slight warmth — minimal visible impairment. At 0.05–0.07%: judgment and coordination begin to decline. At 0.08%: the legal driving limit — significant coordination and reaction time impairment. At 0.10–0.14%: slurred speech, significant motor impairment. At 0.15–0.20%: severe impairment, potential nausea. Above 0.25%: risk of blackout, alcohol poisoning, and loss of consciousness. Above 0.35–0.40%: potentially fatal. This calculator is for educational purposes only — never drive after drinking, regardless of estimated BAC.
Inputs
Results
A 170 lb male who consumed 3 drinks over 2 hours is below the 0.08% legal limit but still mildly impaired. About 2.7 hours until BAC reaches zero.
Inputs
Results
A 130 lb female consuming 5 drinks in 1.5 hours reaches ~0.19% BAC — well above the legal limit. Nearly 13 hours to return to zero.
No. This calculator provides a rough estimate based on population averages. Individual BAC can vary by 30–50% from the Widmark estimate due to factors like food intake, gastric emptying rate, individual metabolic rate, medications, and liver health. The only way to know your actual BAC is with a calibrated breathalyzer or blood test. Never use this calculator — or any calculator — to decide whether you are safe to drive.
Females generally have a lower volume of distribution for alcohol because of higher average body fat percentage and lower total body water. Adipose tissue contains very little water, so alcohol is distributed in a smaller volume, resulting in higher BAC per drink. Additionally, females typically have lower levels of alcohol dehydrogenase in the stomach, reducing first-pass metabolism before alcohol enters the bloodstream.
Food does not reduce BAC that has already been absorbed — the liver metabolizes alcohol at a constant rate regardless of food intake. However, eating before or during drinking slows gastric emptying and delays alcohol absorption into the bloodstream, reducing the peak BAC achieved. High-fat meals provide the greatest slowing effect. Food can reduce the maximum BAC spike by 20–30% but does not change the total amount of alcohol that must eventually be metabolized.
No. Coffee, cold showers, exercise, or sleep do not increase the rate of alcohol metabolism. The liver metabolizes alcohol at a roughly fixed rate of approximately 0.015% BAC per hour — this cannot be significantly accelerated by any common intervention. Coffee may increase alertness (masking the sedating effects of alcohol) but does not reduce impairment. Only time will lower BAC.
In the United States, the legal BAC limit for adult drivers is 0.08% in all 50 states. For drivers under 21, the limit is typically 0.00–0.02% (zero-tolerance laws). For commercial vehicle drivers, the limit is 0.04%. Many countries have lower limits — 0.05% is the standard in most of Europe, and 0.02% is the limit in Sweden, Norway, and Poland. At any measurable BAC, driving ability is compromised to some degree.
Alcohol poisoning is a medical emergency caused by a very high BAC, typically above 0.25–0.30%. Signs include: mental confusion, vomiting, seizures, slow or irregular breathing (fewer than 8 breaths/min), blue-tinged skin, and unconsciousness that cannot be aroused. If you suspect alcohol poisoning, call 911 immediately. Do not leave the person alone, do not give them coffee or cold water, and place them in the recovery position to prevent aspiration if they vomit.
How helpful was this calculator?
5.0/5 (1 rating)
