BAC Calculator Online
Estimate blood alcohol content from drinks, weight, sex, and time using the Widmark formula, right in your browser. A rough estimate only, not medical advice — never use it to decide if you can drive.
The BAC Calculator runs entirely in your browser. The weight, drinks, and time you enter never leave your device and nothing is uploaded to ArrayKit. Results are a general estimate using a standard formula, not medical advice — never use them to decide if you can drive.
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About BAC Calculator
BAC Calculator estimates blood alcohol content from the number of standard drinks you have had, your body weight, your sex, and the hours elapsed since your first drink, using the Widmark formula that DUI-education and public-health resources rely on. It shows the estimated BAC as a percentage and flags whether it is at or above the common 0.08% legal driving limit. It is handy for understanding roughly how alcohol and time affect BAC, or for comparing scenarios like weight or drink count. Everything computes instantly on your device — your figures are never uploaded. This is a general estimate using a standard formula, not medical advice, and it must never be used to decide whether you are okay to drive — do not drive after drinking.
Features
- Estimates BAC from standard drinks, body weight, sex, and hours elapsed
- Uses the Widmark formula, the standard estimate for blood alcohol content
- Separate distribution ratios for male and female bodies
- Flags when the estimate reaches the common 0.08% legal driving limit
- Accounts for the body's average alcohol elimination rate over time
- Copy a plain-text summary of the inputs and estimated BAC
- Instant results as you type, with no page reloads
- Runs entirely in your browser — your figures never leave your device
How to use the BAC Calculator
- Enter your body weight in kilograms
- Select your sex
- Enter the number of standard drinks and hours since the first one
- Read the estimated BAC and legal-limit flag
Example
Input
70kg male, 3 drinks, 2h
Output
BAC: ~0.04%
The Widmark formula estimates a BAC of roughly 0.04% for this example.
Common errors & troubleshooting
- BAC Calculator shows an error even though numbers were entered. — Make sure weight is greater than 0, and that the drink count and hours are 0 or more — negative values are not valid.
- Estimated BAC seems too high or too low compared to how a person feels. — The Widmark formula is a population average — food, medication, hydration, and individual metabolism can shift real BAC well away from the estimate, so treat it as a rough guide only.
- Result changes noticeably when switching sex. — The Widmark formula uses a different distribution ratio for male and female bodies, so double-check the selected sex matches the person the estimate is for.
- BAC Calculator shows 0.000% after a long gap. — The formula subtracts an average elimination rate for every hour elapsed, so a low result after many hours means the estimate has fully cleared — it is clamped at zero and never goes negative.
Frequently asked questions
- What formula does the BAC Calculator use?
- It uses the Widmark formula, which estimates blood alcohol content from the grams of alcohol consumed, body weight, a sex-based distribution ratio, and an average elimination rate applied per hour elapsed.
- How many grams of alcohol does the BAC Calculator assume per drink?
- It assumes 14 grams of pure alcohol per standard drink, the common US standard-drink measure (roughly one 12oz beer, 5oz wine, or 1.5oz spirits).
- Can the BAC Calculator tell me if I am safe to drive?
- No. It gives a rough estimate only, using a standard formula. It must never be used to decide whether you are okay to drive — always err on the side of caution and do not drive after drinking.
- Why does the BAC Calculator give a different result for male and female at the same weight?
- The Widmark formula uses a lower body-water distribution ratio for female bodies, which spreads the same amount of alcohol through less fluid, producing a higher estimated BAC at the same weight and drink count.
- Is the BAC Calculator's estimate medical advice?
- No. It is a general estimate using a standard formula, not medical advice. Actual BAC varies with food intake, medication, hydration, and individual metabolism.
- Is my weight or drink count uploaded when I use the BAC Calculator?
- No. The BAC Calculator runs entirely in your browser. The numbers you type are used only to compute the estimate on your device and are never sent to ArrayKit or anywhere else.
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