Blood alcohol calculator for drinks, body weight and elapsed time
Add common U.S. serving examples or enter the labels from the drinks you actually had, then see how the Widmark estimate changes with body weight, distribution factor, and elapsed time. The state-law card is context only, never a safe-driving target.
Enter drink details
Preset buttons add to the running total. For more than one drink, add each serving and then check the combined volume and ABV against the containers or pours you had.
Widmark estimate
Enter body weight and drink details to see pure alcohol, initial BAC, and the elapsed-time deduction.
- Pure alcohol
- —
- Initial BAC estimate
- —
- Elapsed-time deduction
- —
- Arithmetic time to zero
- —
Common state per-se threshold reference
0.08 g/dL in most states; 0.05 g/dL in UtahThe CDC page reviewed January 28, 2026 says every state except Utah uses 0.08 g/dL as the per-se threshold, while Utah uses 0.05 g/dL. Impairment begins below those numbers, and lower limits or separate rules can apply by state, driver age, or license class. This is not one universal U.S. legal limit, and a calculator result below the line is not permission to drive.
CDC · Impaired Driving · 2026-09-02This output is a Widmark estimate, not a measurement. The 0.68 and 0.55 factors are population averages rather than personal physiology, and time to zero is arithmetic based on one fixed elimination rate rather than proof of sobriety. The legal reference is not permission to drive.
ready to use.
- Visible firstKeep the input and result positions clear.
- Results firstPut the main number up front and keep the process secondary.
- Less to askNo sign-up or extra information before using the tool.
How to read a blood alcohol estimate without treating it as a test
Two people can drink the same beverage and follow very different BAC curves. Food, drinking pace, absorption, body water, and health all shape the measured result, while a short form cannot capture them. This calculator converts the ethanol in a drink to grams and applies the Widmark equation so that you can compare the scale of different inputs, not certify an individual BAC.
The initial estimate, elapsed-time deduction, current estimate, and time-to-zero number all come from one simplified model. The sections below follow the calculation from volume and ABV through density, body weight, distribution factor, and average elimination, then explain cumulative presets, unit conversion, U.S. threshold context, and the action to take when safety matters.
What the Widmark calculation does
The calculator first isolates the ethanol portion of the drink, converts that volume to mass, and divides the mass by body weight and a distribution factor. That creates an initial BAC estimate under the simplified assumption that absorption is complete. It then subtracts an average amount for elapsed time. Because it does not reproduce an individual absorption curve, the output is an approximation rather than a reading.
- Ethanol volume = drink volume × ABV ÷ 100
- Ethanol mass = ethanol volume × density
- Initial estimate = mass ÷ body weight ÷ distribution factor
- Current estimate = initial estimate − elapsed-time deduction
Converting a pour into grams of pure alcohol
Fluid ounces or milliliters alone do not describe the alcohol dose; ABV must be included. A 12 fl oz beer is about 354.9 mL, and at 5% ABV it contains about 17.7 mL of ethanol. PubChem reports an ethanol density of 0.7893 g/cm³ at 20°C from a peer-reviewed handbook source. The tool rounds it to 0.789 g/mL, producing about 14.0 g of pure alcohol in this example.
- Check the container volume and ABV rather than guessing by drink name
- 5% ABV means 5% of the beverage volume is ethanol
- 17.7 mL × 0.789 g/mL is about 14.0 g
- Pure alcohol grams make different drink types easier to compare
A distribution factor is not personal physiology
The historical 0.68 and 0.55 factors approximate how alcohol is distributed in broad populations. They cannot encode individual body water, body composition, age, health, or day-to-day conditions. Since the factor sits in the denominator, switching it changes the estimate materially. Treat that movement as evidence of model uncertainty, not as a choice between two exact biological profiles.
- A smaller factor produces a higher estimate with the same inputs
- The buttons do not determine sex or measure body composition
- Running both factors is a sensitivity check, not a guaranteed personal range
- Legal or medical decisions require actual evidence, not a chosen average
Elapsed time is a straight-line arithmetic deduction
The tool subtracts 0.15 g/L per hour, shown as 0.015 percentage points of BAC per hour. A forensic review found physiological elimination rates from about 0.10 to 0.35 g/L per hour, so a fixed line cannot predict a person precisely. BAC may also continue rising while alcohol is still being absorbed, even though time has passed since the first drink.
- Elapsed hours × 0.015 percentage points is subtracted
- A negative result is displayed as zero
- Displayed zero does not verify that no alcohol remains
- Coffee, showers, exercise, and sleep do not guarantee a faster rate
Preset drinks build one cumulative total
The four buttons reflect familiar U.S. package or pour sizes, including a stronger 16 fl oz beer. They are convenient examples rather than official standard-drink claims, and real products vary. Every click adds ethanol to the existing total, so mixed drinks can be represented by adding their actual components or entering the combined amount and ABV carefully.
- Two clicks on 12 fl oz beer add two servings to the total
- Beer, wine, and spirits are converted to grams before being combined
- A home pour may be larger than the 1.5 fl oz spirits example
- Check the running total after each addition and reset mistakes
Unit conversion should not change the substance
English defaults to pounds and U.S. fluid ounces, while kg and mL remain available. Internally, 1 lb is converted to 0.45359237 kg and 1 U.S. fl oz to 29.5735 mL before the formula runs. Correctly paired numbers and units produce the same result. Most large unit errors come from entering an already converted value under the other unit.
- 154.3 lb is about 70 kg
- 12 U.S. fl oz is about 354.9 mL
- Enter 5 for 5% ABV, not 0.05
- Recheck the selected unit whenever a number is pasted
Initial, current, and time to zero answer different questions
Initial BAC is the model value after assuming the entered ethanol has been absorbed. Current BAC subtracts the fixed average for the elapsed hours. Time to zero divides the remaining estimate by that same rate. These numbers explain the model, but none establish the peak time, a breath or blood measurement, actual sobriety, or fitness to drive.
- Initial estimate does not model when the peak occurs
- Current estimate depends directly on the elapsed-time assumption
- Time to zero is arithmetic, not a guaranteed sober time
- Feeling normal does not show that reaction and judgment are unimpaired
Reading the U.S. reference without inventing one national limit
The CDC says every state except Utah uses 0.08 g/dL as a per-se threshold, while Utah uses 0.05 g/dL. That makes 0.08 a common state reference, not a single federal permission line. Driver age, commercial licensing, state-specific offenses, observable impairment, and case facts can change what applies. The calculator cannot determine any of them.
- 0.08 g/dL is the common state per-se threshold
- Utah uses 0.05 g/dL
- Impairment begins below either displayed number
- Rules for underage or commercial drivers can be lower or separate
- An estimate below a line is never a clearance to drive
Choose a safe action before looking for a favorable number
After drinking, the reliable plan is transportation that does not depend on your estimate: a sober driver, taxi, rideshare, public transit, or staying put. If someone becomes seriously unwell, the priority changes from transportation planning to emergency care. Do not spend that time adjusting inputs or waiting for the displayed number to fall.
- Keep the keys away from anyone who has been drinking
- Watch for inability to wake, repeated vomiting, seizure, or slow and irregular breathing
- Call 911 for emergency signs and stay with the person
- Place an unconscious breathing person on the side when vomiting is possible
- Never have the impaired person drive to seek care
Blood alcohol calculator questions
How close is this BAC estimate to a breath or blood test?
It is not a substitute for either test. The Widmark equation assumes that consumed ethanol distributes in a predictable way and disappears at a steady rate. Real BAC changes with absorption, food, pacing, body water, medication, and health. Research describes Widmark calculations as gross approximations, so the result is not a breathalyzer reading, blood result, diagnosis, or legal evidence.
Should I choose 0.68 or 0.55 for the distribution factor?
Both are historical population-average reference values, not a precise sex selector or a measurement of your body. Body composition and water distribution vary widely among individuals. Running both can show how much this assumption changes the answer, but the two results do not create a guaranteed range for your actual BAC.
Does everyone eliminate alcohol at the same rate?
No. The calculator subtracts 0.15 g/L per hour, equivalent to 0.015 percentage points of BAC per hour, to keep the arithmetic understandable. A published review found physiological rates spanning roughly 0.10 to 0.35 g/L per hour. Coffee, cold showers, food, and exercise do not reliably speed that process, and the personal rate cannot be known from this form.
What happens when I click several drink presets?
Each click adds that example to the cumulative total. The buttons are plausible package and pour sizes, not a claim that every serving is an official standard drink. You can add beer, wine, and spirits in sequence, but confirm the actual ounces and ABV from the label or pour before relying on the total.
Can I mix pounds with milliliters or kilograms with fluid ounces?
Yes. The calculator converts weight to kilograms and volume to milliliters internally, using 1 pound as 0.45359237 kilogram and 1 U.S. fluid ounce as 29.5735 milliliters. The result stays consistent when the selected units match the numbers. A common mistake is entering a pound value while kg is selected or converting ounces twice.
Can alcohol still be present the next morning?
Yes. Sleep does not make alcohol disappear, and a large amount consumed late can remain into the next day. The displayed time to zero is only the current estimate divided by a fixed average elimination rate; it is not the moment a person is actually sober. Do not drive when alcohol may remain or when hangover symptoms affect you.
Does an estimate below 0.08% mean driving is legal?
No. Most states use 0.08 g/dL as a common per-se threshold, but Utah uses 0.05, other rules can apply to particular drivers, and impairment starts at lower levels. The calculator has not measured your BAC and cannot apply every state rule or fact in a case. After drinking, use a sober driver, taxi, rideshare, public transit, or stay where you are.
What should I do if someone is hard to wake after drinking?
Call 911 immediately if the person cannot be awakened, vomits repeatedly, has a seizure, breathes slowly or irregularly, or has pale or blue-tinged skin. Do not wait for the calculator. Stay with the person, do not force coffee or water, and place them on their side if vomiting may block the airway. Do not let an impaired person drive to get help.
Evidence and official references
Checked September 2, 2026. Ethanol density comes from the CRC Handbook value cited by PubChem; formula accuracy and elimination-rate variation come from PubMed-indexed forensic research. U.S. threshold and impairment context follows the CDC page reviewed January 28, 2026. Current references do not turn this estimate into a measurement, legal opinion, or driving clearance.