Calcyx
Health

BAC Calculator - Blood Alcohol Content

Calculate estimated blood alcohol level, drinking window, and time until sober.

Basic Info

Timeline

Drink List

Customize Drinks

Estimated BAC

0.55 ‰

Peak 0.7‰

Estimated Sober In

3.7 h

Sober By

05/27, 08:29 AM

Time since last drink

0 h

Drinking window

Duration 2 h

05/27, 02:48 AM → 05/27, 04:48 AM

Summary

Total Alcohol 35.8 g
Standard Drinks (12g) 3
Total Volume 0.78 L

⚠️ Note

This calculator provides a rough estimate. Actual BAC depends on metabolism, food, medication, and many other factors. Never drive or make risk-based decisions under the influence.

Blood Alcohol Calculator – Calculate BAC

The Blood Alcohol Calculator combines body weight, gender, and drink quantities to quickly estimate your Blood Alcohol Content (BAC). The tool uses the Widmark formula, accounts for the duration of your drinking window, and displays both your current BAC and peak BAC. This gives you an at-a-glance view of when alcohol will likely clear your system and when your BAC returns to zero.

Overview

This BAC calculator is designed with features that work universally: it follows commonly used BAC limits, uses kilograms and liters, and presents results in clear English. The interface works equally well for a quick check or modeling an entire evening's progression – you can add different drinks, adjust their strengths, and set the entire drinking window from start to finish. This makes the calculator a useful planning tool for celebrations or creating a responsible driving plan.

Inputs and Usage

  1. Weight (kg): Enter your weight. The more accurate the value, the more realistic the BAC estimate, as the Widmark factor divides alcohol into body fluids.
  2. Gender: Your choice determines the Widmark coefficient used (0.68 for males on average, 0.55 for females), reflecting body water content.
  3. Start and End Time: Select times using your local timezone. The calculator uses these to compute the drinking window length and how long it's been since your last drink.
  4. Drink List: Add each drink's volume in liters, alcohol by volume (ABV) as a percentage, and quantity. You can name drinks like "beer 4.5%" or "sparkling wine" and use presets to speed up entry.
  5. Viewing Results: See real-time updates of your current BAC estimate, peak BAC reached, estimated hours until zero, and a summary of total alcohol, standard drinks, and drink volume.

How the Calculation Works

The calculator converts each drink's volume to milliliters, multiplies by ABV and ethanol density (0.789 g/ml) to get grams of alcohol. Total grams are divided by the Widmark factor and body weight to yield theoretical peak BAC. Since the body burns alcohol even while drinking, the model subtracts half the elimination rate during the drinking window (0.15 ‰/h). Finally, current BAC is calculated by subtracting time elapsed since drinking stopped at the same burn rate. This also updates the estimate for reaching zero BAC and the time when you'll be sober again.

Interpreting Results

The calculator's key numbers are peak BAC, current BAC, and time to sober. Peak BAC shows how high your BAC climbed with the given drink amount, helping you understand the expected level of intoxication. Current BAC shows your present state, which you can compare to legal limits (for example, 0.5 ‰ for DUI and 1.2 ‰ for aggravated DUI in many jurisdictions). The sobriety time and "sober by" timestamp help you plan the next day, such as work shifts or travel. Remember that individual variations are significant, so the calculator's numbers are always estimates.

Example Calculation

Imagine an 80 kg male who starts drinking at 6:00 PM and stops at 10:00 PM. He consumes four 0.33 L beers at 4.7%, two 0.12 L glasses of 12% wine, and one 0.04 L shot of 40% spirits. The calculator totals the alcohol as grams (approximately 79 g) and divides by weight and Widmark factor. The result is a peak BAC around 0.9 ‰, while four hours after the last drink the estimated BAC is about 0.3 ‰. The calculator also indicates alcohol will burn off to zero by approximately 5:00 AM, allowing safer travel after the night – though always verify how you feel first. The example shows how drink quantity, strength, and timing affect the outcome.

Limitations and Disclaimer

The Blood Alcohol Calculator is intended for responsible self-assessment, not medical or legal decision-making. Actual BAC depends on numerous factors: liver health, hormone function, sleep, stress, medications, food intake, and the order drinks are consumed. Measurement timing and entered values may also have inaccuracies. Never use the calculator's result as the final measure of fitness to drive or work. When in doubt, always choose the safest option, avoid driving, and use public transport or rideshares. Remember that the best decisions come from moderation: plan your drinks, take breaks, and drink water between alcoholic beverages. This way, the BAC calculator serves as a partner in more responsible alcohol use.