How to Use
- 1.
Select the male or female Widmark body-water reference and enter weight.
- 2.
Optionally enter age and choose the relevant US driving-law reference.
- 3.
Add each drink group with type, quantity, serving size, ABV, and approximate hours ago.
- 4.
Review the estimated current BAC, peak estimate, and elimination timeline.
- 5.
Treat every time result as an educational estimate, never permission to drive.
- 6.
Call 911 immediately if anyone shows signs of alcohol overdose.
Features
Simplified Widmark BAC estimate
Pounds and kilograms toggle
Beer, wine, spirits, cocktail, and custom entries
Multiple drink groups and consumption times
Editable serving size and ABV
US standard-drink conversion
Average 0.015% hourly elimination reference
Estimated time to 0.00%
Most-state, Utah, commercial, and under-21 references
BAC elimination timeline graph
BAC effects reference chart
Food absorption context without unsafe discounting
Copy, share, print, and save-as-PDF support
Alcohol-overdose emergency guidance
SAMHSA National Helpline resource
Critical do-not-drive disclaimer
Frequently Asked Questions
How does this BAC calculator work?+
It applies a simplified Widmark-style estimate to pure alcohol, body weight, a population distribution coefficient, and elapsed time, using 0.015 percentage points per hour as an average elimination reference.
Is an online BAC calculator accurate?+
No online calculator can measure BAC. Actual results vary with pour size, absorption, genetics, medications, health, body composition, and metabolism. A valid breath or blood test is required to measure BAC.
Can this calculator tell me when I am safe to drive?+
No. Never use the result to decide whether to drive. Impairment can occur below statutory limits, the estimate can be wrong, and the only safe BAC for driving is zero.
What is the legal BAC limit in the United States?+
NHTSA reports 0.08% as the adult per se limit in most states and 0.05% in Utah. Other laws and lower administrative thresholds can apply, so check current state rules.
What BAC limit applies to commercial drivers?+
FMCSA uses 0.04% for CDL drivers operating commercial motor vehicles and imposes additional safety restrictions at lower alcohol concentrations.
What BAC limit applies to drivers under 21?+
All states have zero-tolerance laws at 0.02% or lower for drivers under 21. Exact rules and penalties vary by state.
How long does BAC take to return to zero?+
The tool divides the estimated current BAC by 0.015% per hour. Individual elimination varies, delayed absorption can occur, and the result must not be used as a driving decision.
Does eating food lower BAC?+
Food can slow absorption when eaten before or while drinking, but it does not remove alcohol already consumed or make driving safe. The calculator therefore does not subtract a food discount from BAC.
Do coffee, cold showers, water, or exercise sober someone up?+
No. These actions do not rapidly metabolize alcohol. Time is required, and a person may remain impaired even if they feel more alert.
What is a US standard drink?+
One US standard drink contains about 0.6 fluid ounces or 14 grams of pure alcohol, roughly 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits.
What are signs of alcohol poisoning?+
Confusion, inability to remain conscious, repeated vomiting, seizures, slow or irregular breathing, clammy or bluish skin, very low temperature, and unresponsiveness are emergency warning signs. Call 911.
Where can someone get help for alcohol use?+
SAMHSA’s National Helpline at 1-800-662-HELP (4357) provides free, confidential treatment referral and information 24/7. Call 911 for a medical emergency.
About this tool
Free Blood Alcohol Content (BAC) Calculator
Use this Blood Alcohol Content (BAC) Calculator to create a rough educational estimate from body weight, a population body-water coefficient, drink volume, alcohol by volume, quantity, and elapsed time. It supports beer, wine, spirits, cocktails, custom drink groups, metric or US weight, multiple drink times, and several US driving-law references.
How the BAC Calculator Estimates Blood Alcohol Content
The calculator uses a simplified Widmark-style equation. It converts each drink into fluid ounces of pure alcohol, estimates alcohol distribution from weight and the selected male or female population reference, then subtracts an average elimination rate of 0.015 percentage points per hour. The result is not a measurement. Only a valid breath or blood test can measure BAC, and individual metabolism can be meaningfully faster or slower than the assumed rate.
Drink Size, ABV, and US Standard Drinks
A US standard drink contains about 0.6 fluid ounces or 14 grams of pure alcohol. Common examples are 12 fluid ounces of 5% beer, 5 fluid ounces of 12% wine, or 1.5 fluid ounces of 40% distilled spirits. Real servings vary. A strong beer, large wine pour, or cocktail can contain two or more standard drinks, so enter the actual container size and label ABV whenever possible.
Multiple Drinks and Drinking Timeline
Add separate drink groups when beverages have different sizes, strengths, quantities, or consumption times. The calculator uses the earliest “hours ago” entry as the session duration for its simplified elimination estimate. Alcohol absorption can continue after the last drink, so real BAC may still be rising even when the graph shows a declining estimate.
Food and Alcohol Absorption
Eating before or while drinking can slow alcohol absorption compared with drinking on an empty stomach, but it does not remove alcohol or guarantee a lower final BAC. For safety, the food selector provides context without artificially reducing the arithmetic result. Coffee, cold showers, water, and exercise do not rapidly eliminate alcohol; metabolism takes time.
Time Until 0.00% and Driving References
The displayed time to 0.00% divides the estimated current BAC by the assumed elimination rate. The comparison time shows when the estimate may fall below a selected legal reference, but it is never a “safe to drive” time. Impairment begins below statutory limits, estimates can be wrong, and state laws or administrative penalties may apply at lower concentrations.
US BAC Laws: 0.08%, Utah 0.05%, Commercial 0.04%
NHTSA states that the adult per se limit is 0.08% in most US states and 0.05% in Utah. FMCSA uses 0.04% for a CDL driver operating a commercial motor vehicle, with additional restrictions below that value. All states have under-21 zero-tolerance laws at 0.02% or lower. Laws change and include more than a BAC number, so check current rules for the relevant state and driver category.
BAC Effects and Alcohol Overdose Warning Signs
Alcohol can impair vision, coordination, judgment, reaction time, and vehicle control before BAC reaches 0.08%. At higher concentrations, vomiting, severe confusion, loss of consciousness, seizures, slow or irregular breathing, and failure of life-support functions can occur. If someone cannot stay awake, is vomiting repeatedly, has a seizure, breathes slowly or irregularly, has clammy or bluish skin, or is unresponsive, call 911 immediately.
Why a BAC Estimate Cannot Confirm Driving Safety
No online BAC calculator can account for all differences in genetics, liver function, medicines, health conditions, body composition, tolerance, pour size, absorption, or timing. Feeling “fine” does not mean driving skills are unimpaired. The safest plan after drinking is to avoid driving and use a sober driver, taxi, rideshare, or other safe transportation.
Alcohol Support Resources
Anyone concerned about their own drinking or someone else’s can contact SAMHSA’s National Helpline at 1-800-662-HELP (4357). The service provides free and confidential treatment referral and information in English and Spanish, 24 hours a day. Call 911 for a medical emergency.
For general nutrition planning unrelated to sobriety, estimate daily energy needs with the Calorie Needs Calculator or plan everyday hydration with the Water Intake Calculator. Food, water, coffee, and exercise do not quickly remove alcohol or make driving safe. Browse other transparent planning tools in the Calculators category.