Blood Alcohol Calculator
A Widmark estimate of BAC, with the legal limits.
Blood Alcohol Calculator estimates blood alcohol concentration with the Widmark equation from drinks, body weight, a Widmark factor and time elapsed. Enter drinks by type and size or as units, see the estimate fall hour by hour, and compare it with driving limits in several countries. Nothing is uploaded.
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Runs entirely on your device. No file or text you enter here is uploaded. How to verify it.
This is a calculation tool, not medical advice. The result is an estimate from a published formula and cannot account for your individual circumstances. Talk to a healthcare professional about anything that matters.
How to use Blood Alcohol Calculator
- Add the drinks by type and size, or enter units or standard drinks.
- Enter your body weight and how long ago the first drink was.
- Read the estimate, the falling curve, and the limits table beside it.
Questions about Blood Alcohol Calculator
Can I use this to decide whether to drive?
No. The only amount of alcohol that is safe before driving is none. This is an estimate with a wide margin, it is not a breath test, and it has no standing with a police officer, an employer or a court. Alcohol impairs judgement and reaction time well below every legal limit on the table.
How wrong can the estimate be?
Wrong enough to matter. Widmark assumes every drink is already in the bloodstream, but absorption takes roughly 30 to 90 minutes and food slows it further, so soon after a drink the figure reads high. The elimination rate varies between people by more than a factor of two. Real measurements routinely differ by several hundredths of a percent, which is the whole distance between two legal limits.
What is the Widmark factor?
It is the fraction of the body that alcohol distributes into — body water, roughly. The values derived by Widmark were 0.68 for men and 0.55 for women, which is why the same drinks produce different results. Body composition moves it more than sex does, so two people of the same weight can end an evening a long way apart.
Does coffee, food or a cold shower speed it up?
No. The liver removes alcohol at a rate that is close to fixed, around 0.015 percentage points of BAC per hour, and nothing you can do at the table changes it. Food eaten before or during drinking slows absorption, which lowers the peak, but it does not shorten the time to zero once the alcohol is in.
Is what I enter here private?
Yes. Drinks, weight and times are read by JavaScript in your own tab and used to fill in the formula. Nothing is uploaded, logged or written to storage beyond your unit preferences, and there is no account for any of it to attach to.
Is Blood Alcohol Calculator really free, with no limits?
Yes. There is no account, no daily cap, no file-size tier and no watermark, because there is no server cost to recover. The site is funded by clearly disclosed partner recommendations on the Partners page, never by metering the tools.
Are my files or text uploaded when I use Blood Alcohol Calculator?
No. Everything is processed by JavaScript running in your browser, on your device. You can verify it: open your browser's developer tools, switch to the Network tab, and use the tool. You will see no request carrying your data — because there is nowhere for it to go.