BAC Calculator
Estimate blood alcohol concentration and time to sober using the Widmark formula. Know your BAC after drinks responsibly.
Estimated BAC
0.052%
42 g of alcohol
Time to zero BAC
≈ 5.5 hours
Elimination is only approximate
Readout
At or above India's 0.03% legal driving limit — do not drive.
Widmark-style estimate only — real BAC depends on food, medications and metabolism. India's legal driving limit is 0.03%. If you have been drinking, do not drive.
Last updated: March 2026
How this calculator is verified
Checked by True Calculator automated test suite on
- Formula verified against a published worked example in the automated test suite
- Edge cases (zero, negative, boundary and unit-mismatch inputs) covered by unit tests
The full verification method is on our how we verify page. Found an error? Tell us and we will re-check it.
When to Use This Calculator
Use the BAC calculator for personal awareness around drinking — for example, before deciding whether to drive after a gathering, or to understand roughly how many hours you need before you are likely to be under India's 0.03% legal limit. It is also useful for students studying pharmacology or forensic science, since the Widmark equation is the classic model of alcohol distribution and elimination. For frequent social drinkers, the 'time to zero' number is a powerful planning aid: it shows why a late evening can keep you over the limit until mid-morning, and why designated drivers are the real solution. The estimate is educational only and will always err on the side of caution in its interpretation.
How to Use This Calculator
- Step 1: Choose your gender.
- Step 2: Enter your body weight in kilograms — it directly affects the BAC result.
- Step 3: Enter the number of standard drinks and the hours since your first drink.
- Step 4: Read your estimated BAC, the sobering time, and how it compares with India's 0.03% driving limit.
Worked Example
A 75 kg man who has three standard drinks (42 g of alcohol) over two hours gets an estimated BAC of 0.052% from the Widmark formula — comfortably above India's 0.03% driving limit, so he must not drive. His estimated time to reach zero is about 5.5 hours from the first drink. A single drink for a 70 kg man after one hour gives 0.014%, below the limit but still impairing. The formula uses a distribution factor of 0.68 for men and 0.55 for women, which is why equal drinks produce higher BAC in women.
Tips and Common Mistakes
- •Tip 1: Remember that Indian pegs and large 'quarter' servings often exceed one standard drink, raising real BAC.
- •Tip 2: The safest rule for driving is zero: the 0.03% limit is reached faster than most people think.
- •Tip 3: Food slows absorption but does not remove alcohol — the sobering time still applies.
- ✗Mistake 1: Using this estimate to decide if you are fit to drive — no formula beats a breath analyser.
- ✗Mistake 2: Assuming coffee, sleep or a shower 'sobers you up' — only time clears alcohol from the body.
Frequently Asked Questions
What is the formula behind the BAC estimate?
The Widmark equation: BAC = (grams of alcohol ÷ (body weight in kg × distribution factor)) × 0.1 − 0.015 × hours since drinking. The distribution factor is 0.68 for men and 0.55 for women.
What counts as one standard drink?
Roughly 14 g of pure alcohol — about 330 ml of 5% beer, 120 ml of wine, or 30 ml of whisky. Indian pegs and local serving sizes are often larger, which raises the real BAC above the estimate.
What is India's legal driving limit?
The legal limit for driving in India is 30 mg of alcohol per 100 ml of blood, which is 0.03%. Many people exceed it after just one peg, so the safest rule is: if you drank, don't drive.
Why is my estimated sobering time so long?
The body clears alcohol at roughly 0.015% per hour regardless of coffee or food. That is why one heavy evening can keep you over the limit well into the next morning — and why a breath analyser is the only real check.
How accurate is this estimate?
It is an approximation. Food in the stomach, medicines, fatigue and individual metabolism all change real BAC. The estimate is a planning tool, not evidence — never rely on it to decide if you are fit to drive.
Compare these tools
- BMI Calculator — Calculate your Body Mass Index instantly and see your WHO weight category
You might also need
Related calculators from other categories
Science & Weather
Acceleration Calculator
Calculate acceleration from initial and final velocity over time, plus the distance covered. Handles speeding up and braking.
Developer
Bandwidth Calculator – File Transfer Time & Speed
Calculate file transfer time from file size and connection speed, or the speed needed for a target time. Supports KB to TB sizes, kbps to Gbps, SI units.
Finance
Credit Card Payoff Calculator
See how extra payments speed up credit card payoff and cut interest. Compare against minimum payments to plan your debt-free date.
Developer
Download Time Calculator
Estimate how long a file takes to download at your connection speed, shown as hours, minutes and seconds.