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Estimated blood alcohol concentration (Widmark formula)

Estimates blood alcohol concentration after drinking using the Widmark formula, for teaching, counselling and retrospective forensic assessment, with Brazilian legal limits.

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Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.

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Method · Limits of application

Local Widmark: r 0.68/0.55 L/kg; elimination 0.15 g/L/h; density 0.789 g/mL; nominal blood/breath ratio 2000:1 in the same unit; numeric conversion g/L ÷ 2 → mg/L.

The Posey/Mozayani 2007 reference discusses estimates for drinking scenarios and retrograde extrapolation, with variability between models and effects of gastrointestinal absorption. The local calculation does not automatically incorporate the six models discussed in the article; individual distribution and elimination factors were not confirmed in this reading of the abstract.

Conditions of use

Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.

Documented parameters

Sex
Weight · kg
Cans of beer (350 mL, 5%) · cans
Glasses of wine (150 mL, 12%) · glasses
Measures of spirits (50 mL, 40%) · servings
Other beverage: total volume · mL
Other beverage: alcohol content · % vol.
Time since drinking began · h

5/5 reference cases checked. Numerical tests are not clinical validation.

Sources and documentation

Documented formula

Transcribed from the source or a recorded revision; this is not a clinical recommendation.

Alcohol consumed (g) = volume (mL) × alcohol content (%) / 100 × 0.789 g/mL (ethanol density).

Local Widmark: C = A / (r × P) − β × t, where A = alcohol consumed (g), P = weight (kg), r = distribution factor in L/kg (0.68 for men and 0.55 for women), β = local elimination of 0.15 g/L per hour (documented range 0.10 to 0.20 g/L per hour), and t = hours since drinking began. Because r × P is a volume in L, C is an estimate in g/L of blood. The local model does not estimate individual absorption.

Local nominal breath conversion: g/L of blood ÷ 2 = mg/L of breath. When concentrations use the same unit, the nominal blood/breath ratio is 2000:1; the numeric factor 2 also reflects the conversion from g to mg. The equivalence cited in the documentation of Article 306 of the Brazilian Traffic Code, 6 dg/L of blood (0.6 g/L) = 0.3 mg/L of breath, is retained as documentary context; this estimate is neither an individual measurement nor a legal opinion.

References

Identifier: alcoolemia-estimada

Original clinical content: Brazilian Portuguese.

Method version

Local Widmark: r 0.68/0.55 L/kg; elimination 0.15 g/L/h; density 0.789 g/mL; nominal blood/breath ratio 2000:1 in the same unit; numeric conversion g/L ÷ 2 → mg/L.

alcoolemia-estimada@native-2026-10-05+13260e6263ac

Source for the active edition

The bibliographic edition identifies the source. By itself, it proves neither full conformity of the formula nor clinical approval.

Synthetic cases checked (5)

Synthetic cases for checking the implementation, with no patient data.

Case 1

reference-001

Inputs

Sex: Male
Weight: 70 kg
Cans of beer (350 mL, 5%): 4 cans
Time since drinking began: 2 h

{
  "sexo": "M",
  "peso": 70,
  "cerveja": 4,
  "horas": 2
}

Expected result

{
  "alcohol": 55.23,
  "c0": 1.1603,
  "bac": 0.8603,
  "zero": 5.735
}

Actual result

{
  "alcohol": 55.230000000000004,
  "c0": 1.160294117647059,
  "bac": 0.8602941176470589,
  "zero": 5.73529411764706
}

Case 2

reference-002

Inputs

Sex: Female
Weight: 60 kg
Glasses of wine (150 mL, 12%): 1 glasses
Time since drinking began: 1 h

{
  "sexo": "F",
  "peso": 60,
  "vinho": 1,
  "horas": 1
}

Expected result

{
  "alcohol": 14.202,
  "bac": 0.2804
}

Actual result

{
  "alcohol": 14.202,
  "c0": 0.43036363636363634,
  "bac": 0.28036363636363637,
  "zero": 1.8690909090909091
}

Case 3

reference-003

Inputs

Sex: Male
Weight: 80 kg
Cans of beer (350 mL, 5%): 1 cans
Time since drinking began: 3 h

{
  "sexo": "M",
  "peso": 80,
  "cerveja": 1,
  "horas": 3
}

Expected result

{
  "c0": 0.2538,
  "bac": 0
}

Actual result

{
  "alcohol": 13.807500000000001,
  "c0": 0.2538143382352941,
  "bac": 0,
  "zero": 0
}

Case 4

reference-004

Inputs

Sex: Male
Weight: 80 kg
Other beverage: total volume: 200 mL
Other beverage: alcohol content: 40 % vol.
Time since drinking began: 0 h

{
  "sexo": "M",
  "peso": 80,
  "outro_ml": 200,
  "outro_teor": 40,
  "horas": 0
}

Expected result

{
  "alcohol": 63.12,
  "bac": 1.1603
}

Actual result

{
  "alcohol": 63.120000000000005,
  "c0": 1.1602941176470587,
  "bac": 1.1602941176470587,
  "zero": 7.735294117647058
}

Case 5

reference-005

Inputs

Sex: Male
Weight: 70 kg
Time since drinking began: 1 h

{
  "sexo": "M",
  "peso": 70,
  "horas": 1
}

Expected result

{
  "error": true
}

Code and reproducibility

This tool’s code on GitHub

Download code and tests

Sources, version and reproduction instructions

README

Local installation

Code license: Apache-2.0

Guidelines and conditions

This repository’s license applies to the code. Third-party instruments, questionnaires, data and models remain subject to their owners’ conditions.

The code tests are technical checks. Clinical approval and professional translation review are recorded separately.

Relationship with cancer research

General context — relationship to be defined

A resource for general clinical contexts. This edition does not assign a specific oncological relationship; selecting it for a study requires a justified question, population and purpose.