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Blood Alcohol Content Calculator

Estimate BAC using the Widmark formula. Free online Blood Alcohol Content Calculator for health — instant, accurate results, mobile-friendly, no signup needed.

BAC
0.058235

Derivation

  1. ├── 01Givendrinks = 3, w = 70, sex = male, hours = 2
  2. ├── 02Formulamax(0,14 × t / (1e3 × a × ("male"===n?.68:.55)) × 100-.015 × r)
  3. └── 03Compute BAC0.058235
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§01What is

Understanding the Blood Alcohol Content Calculator

The Blood Alcohol Content Calculator computes BAC from 4 inputs: standard drinks, weight (kg), sex, hours since first drink. Estimate BAC using the Widmark formula.

Health metrics give us objective checkpoints against a body that can feel unreliable. Used alongside professional guidance — not in place of it — these numbers help you track progress and spot trends that matter. The Blood Alcohol Content Calculator sits in that toolkit — it estimate BAC using the Widmark formula. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

max(0,14 × t / (1e3 × a × ("male"===n?.68:.55)) × 100-.015 × r)

Where

drinks
Standard drinks
w
Weight (kg)
sex
Sex — one of: male, female
hours
Hours since first drink
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Standard drinks = 3, Weight (kg) = 70, Sex = male, Hours since first drink = 2.

  1. 01Start by noting the input — Standard drinks: 3.
  2. 02Start by noting the input — Weight (kg): 70.
  3. 03Start by noting the input — Sex: male (a category, not a number).
  4. 04Start by noting the input — Hours since first drink: 2.
  5. 05Substitute these values into the formula: max(0,14 × t / (1e3 × a × ("male"===n?.68:.55)) × 100-.015 × r)
  6. 06Compute BAC: the calculator returns 0.0582353.
  7. 07Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Blood Alcohol Content Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Standard drinks halved

drinks = 1.5 (from 3)

Keep every other input at its default and halve the standard drinks. See how bac responds.

  1. 01New Standard drinks: 1.5
  2. 02Baseline BAC: 0.0582353
  3. 03New BAC: 0.0141176
  4. 04BAC decreases by 75.8% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Standard drinks doubled

drinks = 6 (from 3)

Keep every other input at its default and double the standard drinks. See how bac responds.

  1. 01New Standard drinks: 6
  2. 02Baseline BAC: 0.0582353
  3. 03New BAC: 0.146471
  4. 04BAC increases by 151.5% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Weight (kg) halved

w = 35 (from 70)

Keep every other input at its default and halve the weight (kg). See how bac responds.

  1. 01New Weight (kg): 35
  2. 02Baseline BAC: 0.0582353
  3. 03New BAC: 0.146471
  4. 04BAC increases by 151.5% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Weight (kg) doubled

w = 140 (from 70)

Keep every other input at its default and double the weight (kg). See how bac responds.

  1. 01New Weight (kg): 140
  2. 02Baseline BAC: 0.0582353
  3. 03New BAC: 0.0141176
  4. 04BAC decreases by 75.8% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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