Estimate your Blood Alcohol Content (BAC) using the Widmark formula. Enter your weight, sex, drink details, and time to get an approximate BAC level with impairment descriptions.
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Educational Purposes Only
This calculator provides rough BAC estimates and must not be used to determine if you are fit to drive or operate machinery. Actual BAC depends on many individual factors not captured here. Impairment can occur at any BAC level. Never drink and drive. If you have consumed any alcohol, use a designated driver, rideshare, or taxi.
Estimated BAC
0.000%
Sober / Minimal Effect
Little to no impairment. You may feel slightly relaxed.
BAC Level Gauge
0.000.080.150.30+
Estimated Time Until Sober
Sober
Standard Drinks
3.0
Based on avg. elimination rate of 0.015% BAC/hour
Legal Limits Comparison
Standard driving limit (most US states)
0.08%UNDER
Commercial drivers (CDL)
0.04%UNDER
Under 21 / Zero tolerance states
0.02%UNDER
USDOT safety-sensitive employees
0.04%UNDER
Standard Drink Reference
Drink Type
Serving Size
ABV
Pure Alcohol
Standard Drinks
Regular Beer
12 oz (355 ml)
5%
14g
1.0
Light Beer
12 oz (355 ml)
4.2%
11.8g
0.8
Craft / IPA
12 oz (355 ml)
7-9%
20-25g
1.4-1.8
Wine
5 oz (148 ml)
12%
14g
1.0
Fortified Wine
3.5 oz (103 ml)
17%
14g
1.0
Spirits (shot)
1.5 oz (44 ml)
40%
14g
1.0
Cocktail (mixed)
varies
varies
14-28g
1-2+
BAC Impairment Levels
Sober / Minimal Effect0.00% – 0.02%
Little to no impairment. You may feel slightly relaxed.
Mildly Relaxed0.02% – 0.04%
Slight sense of well-being and relaxation. Minimal impairment of reasoning and memory.
Buzzed0.04% – 0.06%
Feelings of warmth and relaxation. Minor impairment of reasoning, lowered inhibitions.
Impaired0.06% – 0.08%
Reduced coordination, impaired judgment and reasoning. At or near the legal driving limit in most states.
Legally Intoxicated0.08% – 0.10%
Clear deterioration of reaction time and control. Slurred speech likely. Illegal to drive in all US states.
Very Intoxicated0.10% – 0.15%
Significant impairment of motor control. Blurred vision, major loss of balance, and vomiting may occur.
Severely Impaired0.15% – 0.20%
Disorientation and confusion. Difficulty standing or walking. Nausea is common.
Dangerous0.20% – 0.30%
Potential for blackout. Severely impaired motor and mental functions. Risk of loss of consciousness.
Life-Threatening0.30%+
Risk of alcohol poisoning, coma, respiratory failure, and death. Seek emergency medical help immediately.
Disclaimer: This Blood Alcohol Content (BAC) calculator is provided for educational and informational purposes only. Results are approximate estimates based on the Widmark formula and do not account for individual variations in metabolism, food intake, medications, tolerance, liver function, or other factors. This tool should never be used to determine whether you are safe to drive, operate machinery, or engage in any activity that could be impaired by alcohol. The only guaranteed safe level of alcohol consumption before driving is zero. Always designate a sober driver, use rideshare services, or call a taxi if you have consumed any amount of alcohol.
How to Use the Blood Alcohol Calculator
Select your biological sex, enter your body weight (toggle between pounds and kilograms), choose the type and number of drinks you have consumed, and specify how long you were drinking and how much time has passed since your last drink. The calculator instantly estimates your BAC using the Widmark formula and shows your impairment level, legal standing, and estimated time until sober.
Understanding the Widmark Formula
Developed by Swedish professor Erik Widmark in the 1930s, the Widmark formula remains the standard for estimating BAC. It accounts for the total grams of alcohol consumed, body weight, a sex-based distribution ratio (the "r" factor), and the time-based elimination rate. While more sophisticated pharmacokinetic models exist, the Widmark formula provides a practical approximation used in both clinical and forensic settings.
Important Limitations
BAC estimation has inherent limitations. This tool does not account for food in the stomach (which slows absorption), medications (which can amplify impairment), individual metabolic differences, liver health, or tolerance. The elimination rate of 0.015% per hour is an average and can range from 0.010% to 0.020% across individuals. Always err on the side of caution.
Frequently Asked Questions
How does the Widmark formula calculate BAC?+
The Widmark formula estimates BAC as: BAC = (alcohol consumed in grams / (body weight in grams x Widmark r factor)) - (0.015 x hours since drinking). The Widmark r factor accounts for body water distribution differences between sexes (0.68 for men, 0.55 for women). The 0.015 rate represents the average hourly alcohol elimination rate.
What is a 'standard drink' in the US?+
A US standard drink contains approximately 14 grams (0.6 fluid ounces) of pure alcohol. This equals about 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV / 80 proof). Many cocktails and craft beers contain more alcohol than one standard drink.
How accurate is this BAC calculator?+
This calculator provides a rough estimate only. Actual BAC varies based on many factors not accounted for here, including food consumption, medications, liver health, hydration, individual metabolism, genetics, and body composition. Two people of the same weight and sex can have very different BACs after the same number of drinks. Never rely on a calculator to determine if you are safe to drive.
What BAC level is considered legally drunk for driving?+
In the United States, the legal limit for driving is 0.08% BAC for drivers aged 21 and over in all 50 states. Commercial drivers (CDL holders) have a lower limit of 0.04%. Drivers under age 21 face zero-tolerance laws, typically 0.00-0.02% depending on the state. Many countries have lower limits, such as 0.05% in Australia and most of Europe.
How long does it take for alcohol to leave your system?+
On average, the body eliminates alcohol at a rate of about 0.015% BAC per hour, which is roughly equivalent to one standard drink per hour. However, this rate varies between individuals. A person with a BAC of 0.08% would take approximately 5.3 hours to reach 0.00%. There is no way to speed up this process; coffee, cold showers, and exercise do not reduce BAC faster.
Why does body weight affect BAC?+
Alcohol distributes through body water. Larger people generally have more body water to dilute the alcohol, resulting in a lower BAC from the same amount of alcohol. This is also why the Widmark factor differs by sex: men typically have a higher percentage of body water (68%) compared to women (55%), meaning women generally reach a higher BAC from the same amount of alcohol at the same body weight.
Can I use this calculator to know if I am safe to drive?+
No. This calculator is for educational and informational purposes only. It provides rough estimates that can be significantly different from your actual BAC. Impairment can occur well below the legal limit. The only safe amount of alcohol before driving is zero. If you have consumed any alcohol, use a designated driver, rideshare, or taxi.