Blood Alcohol Calculator
Estimate your blood alcohol concentration from what you drank, your body weight and the time since your first drink.
A blood alcohol calculator estimates BAC with the Widmark formula: grams of alcohol divided by body weight times a distribution ratio (0.68 for men, 0.55 for women), minus 0.015 for each hour since you started. A 180-pound man who drinks three beers peaks near 0.076% and is estimated at 0.046% two hours later. It is only an estimate and cannot tell you if you can drive.
This calculator gives a rough estimate for general education only. It is not medical advice or legal advice, it is not a substitute for a breathalyzer or a blood test, and it cannot tell you whether you are fit to drive, work or operate machinery. Your real blood alcohol level can be higher than this estimate. If you have been drinking, do not drive. If someone is confused, vomiting repeatedly, breathing slowly or cannot be woken, call 911 or your local emergency number.
Estimated blood alcohol now
0.046%
- Estimated peak (if all absorbed at once)
- 0.076%
- Alcohol consumed
- 42.0 g
- US standard drinks
- 3.0
- Hours until the estimate reaches zero
- 3.0 hours
Embed this calculator on your site →
About the Blood Alcohol Calculator
This calculator uses the Widmark formula, published by the Swedish chemist Erik Widmark in 1932 and still the basis of most BAC estimates. It works out how many grams of alcohol you drank, spreads them across the water in your body, and subtracts what your liver has cleared since your first drink. A US standard drink holds 14 grams of alcohol, which is roughly one 12-ounce beer at 5%, one 5-ounce glass of wine at 12%, or one 1.5-ounce shot of 40% spirits. The distribution ratio is 0.68 for men and 0.55 for women because women on average carry a higher share of body fat, which holds little alcohol, so the same drinks produce a higher concentration. Elimination is set at 0.015 per hour, a common average; real rates vary from person to person and day to day. The formula assumes every drink was absorbed the moment you had it, so early in an evening the estimate can run ahead of reality, and later it can run behind if you drank quickly or on an empty stomach. Treat the number as a rough guide to how much you have had, never as permission to drive. Coordination and judgment are affected well before the 0.08% limit that applies in most of the US.
Frequently asked questions
How accurate is a blood alcohol calculator?+
Only roughly. The Widmark formula uses population averages for how alcohol spreads through the body and how fast it is cleared. Food, medication, drinking speed, liver health and tolerance all move the real number, and two people with the same weight and drinks can differ widely. A breath or blood test measures; this estimates.
Can I use this to decide if I am okay to drive?+
No. The estimate can be lower than your real level, and impairment begins well below any legal limit. If you have been drinking, arrange another way home. That is the only answer this page will give on driving.
How long does it take for alcohol to leave your body?+
The average rate used here clears 0.015 percentage points of BAC per hour, which for many people is slower than one drink an hour, so a level of 0.046% takes roughly three hours to reach zero. Coffee, water, food after drinking, sleep and cold showers do not speed this up; only time does.
What is a standard drink?+
In the US, a drink with 14 grams of pure alcohol: 12 ounces of 5% beer, 5 ounces of 12% wine, or 1.5 ounces of 40% spirits. Craft beers, large pours and cocktails often hold more than one, which is why the calculator lets you enter a drink's size and strength directly.
Why is the estimate higher for women?+
On average women have less body water per pound than men, and alcohol dissolves in water rather than fat, so the same amount of alcohol ends up more concentrated. The formula captures this with a lower distribution ratio, 0.55 instead of 0.68. It is an average; individuals of either sex can sit well above or below it.
Embed this calculator
Free to use on your own site. Paste this snippet where you want the blood alcohol calculator to appear — it resizes itself automatically.
<iframe
src="https://manytools.co/embed/blood-alcohol-calculator"
title="Blood Alcohol Calculator by ManyTools"
data-manytools="blood-alcohol-calculator"
width="100%"
height="640"
loading="lazy"
style="border:0;width:100%;max-width:720px"></iframe>
<script>
(function () {
window.addEventListener("message", function (e) {
if (e.origin !== "https://manytools.co") return;
var d = e.data || {};
if (d.type !== "manytools:embed:height" || d.slug !== "blood-alcohol-calculator") return;
var f = document.querySelector('iframe[data-manytools="blood-alcohol-calculator"]');
if (f && d.height) f.style.height = d.height + "px";
});
})();
</script><a href="https://manytools.co/health/blood-alcohol-calculator">Blood Alcohol Calculator by ManyTools</a>