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BAC Calculator: Blood Alcohol Content Estimator (Widmark) — Global, Responsive, SEO-Optimized

Blood Alcohol Content (BAC) Calculator

Enter your details

All calculations convert internally for consistent global results.

Drinks consumed

Enter up to five drink types. Use ABV (%) from the label and the volume per drink.

Alcohol contribution by drink

Each segment shows the percentage contribution of a drink type to total alcohol.

What is blood alcohol content (BAC)?

Blood Alcohol Content (BAC) estimates the percentage of alcohol in your bloodstream. For example, 0.05% means 0.05 grams of alcohol per 100 mL of blood. BAC rises as you drink and generally falls as your body metabolizes alcohol over time. Many factors influence BAC, including drink strength, body mass, biological sex, and time since first drink.

BAC estimates help you plan safer choices. They are not guarantees of safety or legality in any situation.

How this calculator estimates BAC

This tool uses the Widmark approach: it converts drink volumes and ABV (%) into grams of pure alcohol, then divides by body water (weight × r constant) to estimate peak BAC, and subtracts a metabolism rate (β) per hour to estimate current BAC. The r constant reflects average body water fractions: approximately 0.68 for male, 0.55 for female, and 0.62 for unspecified. The β value typically ranges from 0.012%–0.020% per hour.

Standard drink and unit conversions

  • Pure alcohol density: 0.789 g/mL. Grams = volume × ABV × 0.789.
  • Metric volumes: mL and % ABV are used directly.
  • Imperial volumes: fluid ounces are converted internally to mL (1 fl oz ≈ 29.5735 mL).

Limitations and responsible use

Individual variation is large. Food intake, medications, health conditions, and drinking patterns matter. Laws differ by location and situation. Use this calculator for education, not to make safety-critical or legal decisions. If in doubt, choose not to drive or operate machinery.

For students and professionals

Students can learn unit conversions, density, and population constants behind Widmark’s formula. Health and safety professionals can use the quick outputs for education, toolbox talks, and awareness campaigns, pairing results with local policies and clinical judgment.

Frequently asked questions

HOW TO use the BAC Calculator?

Select your unit system, enter height, weight, sex, hours since first drink, and drinks (volume, ABV, count). Choose Calculate to see estimated BAC, peak BAC, time to zero, and a 3D chart of alcohol contributions.

HOW TO switch between metric and imperial?

Use the Unit system dropdown. The calculator converts volumes (mL ↔ fl oz) and weights (kg ↔ lb) internally so you can use it anywhere in the world.

HOW TO estimate a standard drink?

A quick rule is 14 g of pure alcohol ≈ one standard drink in some regions. You can also enter ABV (%) and volume directly; the calculator handles the math.

HOW TO lower my BAC safely?

Only time lowers BAC. Hydration, food, or coffee may change how you feel but do not speed up alcohol metabolism. Plan ahead and arrange safe transport.

HOW TO share my results?

Click Share result to copy a URL with your inputs. You can send it to friends or save it for later reference.

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