Quick start
- Open the BAC Calculator.
- Enter drink volume, alcohol by volume, number of drinks, body weight, formula sex, and time since drinking began.
- Use the first example, "Two beers: Male, 80 kg, 2 x 355 mL at 5%, 1 hour", if you want to see a filled-out calculation before entering your own values.
- Calculate, read the formula line, then copy the result only after the units and assumptions look right.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Understand how drink count, ABV, body weight, and time affect an estimate.
- Compare different drink sizes and strengths.
- See why BAC estimates are uncertain.
- Avoid using estimates for legal or safety decisions.
What this calculator is for
The BAC Calculator estimates blood alcohol concentration with a Widmark-style formula. It is for education only and must never be used to decide whether to drive.
Use it when you want to: Understand how drink count, ABV, body weight, and time affect an estimate. Compare different drink sizes and strengths.
What to enter
Good answers start with clean inputs. Before calculating, check the labels, units, and dates so the tool is solving the same problem you actually have.
- Enter drink volume, alcohol by volume, number of drinks, body weight, formula sex, and time since drinking began.
- Use actual ABV and pour size where possible, not guesses.
- Remember that mixed drinks can contain more alcohol than one standard drink.
Example walkthrough
Try the calculator example: Two beers: Male, 80 kg, 2 x 355 mL at 5%, 1 hour. The example result is About 0.0365% BAC; estimated 2.43 hours to zero.
- For two 355 mL beers at 5%, the calculator estimates grams of alcohol first.
- It then applies a body-water factor and subtracts an average elimination amount for elapsed time.
Formula and steps
In plain language: The calculator estimates grams of alcohol from drink volume, ABV, drink count, and 0.789 g/mL ethanol density, applies a Widmark-style body-water factor, then subtracts 0.015 percentage points per hour as a rough elimination estimate. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
Read the formula note when you need to understand where the number came from, especially before comparing results over time.
How to read the answer
BAC estimates are especially uncertain because food, medication, drinking speed, tolerance, and body composition can change real-world results. Never use a BAC estimate to decide whether to drive.
- The estimate can be wrong because absorption, food, medications, health, tolerance, and timing vary.
- A lower estimate does not mean safe or legal to drive.
Common mistakes to avoid
Most bad results come from a small input mistake or from using a rough estimate for a decision it cannot safely answer.
- Do not use the result for driving, work, legal, or safety decisions.
- Do not enter the label serving size if your actual pour was larger.
- Do not assume alcohol leaves the body at the same rate for everyone.
What to try next
A related health tool can help check the same topic from another angle, but one number should not replace proper care.
- Plan transportation before drinking.
- Use official public-health guidance for alcohol safety questions.
Sources and safety notes
This guide uses public-health, clinical, or peer-reviewed references where the calculator needs a specific formula or interpretation boundary.
Source links are provided for transparency, but they do not turn the calculator into medical advice or a replacement for professional care.
Worked examples for BAC Calculator
About 0.0365% BAC; estimated 2.43 hours to zero
About 0.0495% BAC; estimated 3.3 hours to zero
About 0.0082% BAC; estimated 0.55 hours to zero
FAQ in plain language
When should I use the BAC Calculator?
Use it for simple educational checks, trend tracking, or planning tasks like these: Understand how drink count, ABV, body weight, and time affect an estimate. Compare different drink sizes and strengths. It can help you understand a number, but it cannot explain your whole health situation.
What do the main BAC Calculator inputs mean?
Enter the formula sex setting, body weight in kilograms, number of drinks, drink size in milliliters, ABV percent, and hours since the first drink. Use the actual pour size and alcohol percentage when you know them. A strong mixed drink or large pour can count as more alcohol than one ordinary serving.
What is the BAC Calculator doing with my inputs?
In plain language: The calculator estimates grams of alcohol from drink volume, ABV, drink count, and 0.789 g/mL ethanol density, applies a Widmark-style body-water factor, then subtracts 0.015 percentage points per hour as a rough elimination estimate. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
How should I read the BAC Calculator result?
Read BAC as a rough educational estimate for the inputs you typed, not as a legal, medical, workplace, or driving decision. Real BAC can differ because food, drinking speed, medications, tolerance, health, body composition, and test timing all matter.
Can I use this BAC estimate to decide whether to drive?
No. Do not use this calculator to decide whether it is safe or legal to drive. Laws, enforcement tests, body differences, medication, food, timing, and impairment can all matter, so the safest practical answer is not to drive after drinking.
What does Widmark-style mean on this page?
It means the calculator estimates grams of alcohol, divides by body weight and a broad body-water factor, then subtracts an average elimination amount for elapsed time. It is a learning estimate, not a breathalyzer, blood test, or legal standard.
Why do drink size and ABV matter so much?
The alcohol grams come directly from volume and ABV. A large craft beer, heavy wine pour, or strong mixed drink can contain much more alcohol than a small standard serving, so entering the label and pour size matters more than the drink name.
Related tools
- Calorie CalculatorEstimate daily calories from BMR, activity level, and goal.
- BMI CalculatorEstimate adult body mass index and healthy BMI weight range.
- Body Surface Area CalculatorEstimate adult body surface area with Mosteller and Du Bois formula results.
Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Health & FitnessBrowse the full category for related tools that help with the same job.
- All free toolsSearch the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guidesFind more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resourcesStart here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.