Blood Alcohol Calculator

BAC Calculator - Blood Alcohol Level

BAC Calculator ﹣ Calculator

With the BAC Calculator, you can calculate your per-mille value, i.e., the blood alcohol concentration (BAC) after the consumption of alcoholic beverages, based on weight, body height and gender, as well as the consumed beverages.

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Supplementary Information on the Blood Alcohol Calculator

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The Calculation Logic of the Alcohol Calculator

The calculation logic of the BAC calculator combines – as does that of the German Federal Centre for Health Education (BZgA) and other international organisations – the formula of Seidl et al. (2000) with the Widmark formula in order to obtain results that are as individual as possible. In addition to the pure display of the blood alcohol content, the result contains extensive explanations of the individual calculation steps. Charts of the calculated blood alcohol level and the breakdown of the alcohol consumed illustrate the result.

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What is the Widmark Formula?

The Swedish chemist Erik M. P. Widmark developed the Widmark Formula for determining the theoretical maximum blood alcohol concentration:

The Widmark formula is

w = A / (m * r)

where

w = the mass fraction of alcohol in the body in ‰
A = the mass of alcohol absorbed in grams (g)
m = the mass of the person in kilograms (kg)
r = the reduction or distribution factor in the body:

  • Men: 0.68–0.7
  • Women/Youth: 0.55–0.60
  • Babies/Toddlers: 0.75–0.80
Our BAC calculator combines this Widmark formula with the formula of Seidl et al.

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Input Aids for the Blood Alcohol Calculator

Please note that the calculation of the blood alcohol concentration (BAC) is without guarantee and is not used to decide whether you can still drive a vehicle. The BAC is dependent on the individual’s physical condition, medication & treatment, etc. and may therefore differ greatly from the results presented here in individual cases. Sometimes BAC is also referred to as "blood alcohol content" instead of "blood alcohol concentration".

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Units of measurement

BAC Calculator Units of measurement Please select the appropriate units of measurement.

US/UK

By selecting 'US/UK', Anglo-American units of measurement are taken into account. Pounds (lbs) are used for weight, and feet (ft) or inches (in) are used for height.

Metric

After selecting 'Metric', metric units of measurement are taken into account. Kilograms (kg) are used for weight, and centimeters (cm) are used for height.

Weight in lbs

BAC Calculator Weight in lbs

Please state your weight in lbs. Blood alcohol content is a measure of the amount of alcohol in the blood. It is calculated as the ratio of the weight of alcohol to body weight, i.e., measured in the metric units g/kg (One gram is approximately equal to 0.56 drams, and one kilogram is 2.2 pounds.) Thus, one gram of alcohol per kilogram of body weight is equivalent to 1.0 g/kg or 1.0 per mille (1‰) of an alcohol content in the blood.

Height in feet and inches

BAC Calculator Height in feet and inches Please state your height in feet and inches. The body weight in relation to the body height forms the basis for calculating the individual body fat percentage. Since alcohol is distributed primarily in the body water after ingestion, with little accumulation in the adipose tissue, body size is an important factor in calculating the blood alcohol content.

Weight in kg

BAC Calculator Weight in kg Please enter your weight in kg. The blood alcohol content is a measure of the amount of alcohol in the blood. It is measured as the ratio of the weight of alcohol to the body weight, i.e., in g/kg. Thus, one gram of alcohol per kilogram of body weight corresponds to an alcohol content in the blood of 1.0 g/kg or 1.0 per mille (1‰).

Height in cm

BAC Calculator Height in cm Please enter your height in cm. The body weight in relation to the body height forms the basis for calculating the individual body fat percentage. Since alcohol is distributed primarily in the body water after ingestion and only a small amount accumulates in fatty tissue, the body height is an important factor in calculating the blood alcohol content.

Gender

BAC Calculator Gender Please indicate your gender. Women usually have a slightly higher individual body fat percentage than men. Since alcohol is distributed mainly in the body water after ingestion and only a small amount accumulates in the fatty tissue, gender is also an important factor in calculating the blood alcohol content, in addition to body height.

Duration of consumption

BAC Calculator Duration of consumption Please indicate how much time has elapsed since the first alcohol was consumed. Since the body not only absorbs alcohol during this time but also breaks it down again, this time period must be taken into account when calculating the blood alcohol content.

Consumed drinks

BAC Calculator Consumed drinks Here, you can select different drinks, record their alcohol content and record the amount consumed. The BAC Calculator adds up the alcohol content of all drinks and calculates your current alcohol level on the basis of the other individual entries. Please select a drink and enter the alcohol content in percent and the consumed amount . With the help of the "Add beverage" button, you can add more drinks. With the help of the “trash” button, you can delete drinks that have already been specified.

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Sample Calculation for the BAC Calculator

Please note that the calculation of the blood alcohol concentration (BAC) is without guarantee and is not used to decide whether you can still drive a vehicle. The BAC depends on the individual's physical condition, medication intake, etc. and can therefore differ greatly in individual cases, as shown in the results here.

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Weight

Ms Kirsch (1.70 m tall, 60 kg or 5 feet, 7 inches tall and 132 lbs is spending a nice evening with her colleagues. They meet at 8 p.m. and toast to a nice evening with a glass of sparkling wine (about 0.1 liter or about 3.5 fluid ounces ) During the course of the evening, she drinks another three glasses of wine at 0.15 liters (about 5 fluid ounces) each.

Around 11 p.m., everyone says goodbye, and Ms Kirsch wants to know how high her blood alcohol concentration (BAC) was at the time. In summary, Ms Kirsch has thus drunk a total of 0.55 liters (approx. 18.5 fluid ounces) of approximately 11-percent alcohol in the last 3 hours.

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Calculation of the amount of alcohol in grams

BAC is measured as the ratio of the amount of alcohol to body weight in metric units (g/kg). Thus, one gram of alcohol per kilogram of body weight is equal to 1.0 ‰ (One gram is equivalent to about 0.56 dram, and one kilogram is 2.2 pounds.) Ms. Kirsch has consumed 60.50 ml ((approximately 2.05 fluid ounces) of alcohol in the last three hours. Since the specific gravity of alcohol is 0.8 g/ml, the amount of alcohol is 48.40 g ((about 27.3 dr). .

Alcohol consumed by Ms Kirsch: conversion from ml to g
60.5 ml alcohol × 0.8 = 48.4 g
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Determination of the theoretical BAC

The theoretical alcohol content in the blood to be determined first depends on its distribution in the body. Since alcohol is exclusively water-soluble, it is not distributed in the bones and fatty tissue. Therefore, this body mass fraction is not available. The Widmark formula for calculating BAC, which has been in use since 1932, therefore distinguishes between women and men. The formula is:

Widmark formula for determining the theoretical BAC
Amount of alcohol / (body weight in kg × r)

(1 kg is about 2.2 lbs)

Here, r is the so-called reduction factor, which is 0.7 for men. Women generally have more fatty tissue; here, it is assumed that r = 0.6.

Widmark reduction factor r
Women0.6
Men0.7

The calculation method for residual alcohol or blood alcohol used in this alcohol calculator is from Seidl et al. BAC takes into account not only gender-specific characteristics and body weight, but also body height. By combining Seidl with the Widmark formula, an individual reduction factor can be calculated, which provides more realistic estimates of BAC according to Widmark, who uses constant factors.

Reduction factor r from Seidl et al.
Women r = 0.31223 - 0.006446 * Weight in kg + 0.004466 * Height in cm
Men r = 0.31608 - 0.004821 * Weight in kg + 0.004432 * Height in cm

Ms Kirsch's distribution factor is r ≈ 0.68. Therefore, the theoretical BAC is 1.18 per mille.

Theoretical BAC by Ms Kirsch
48.4 g / (60 × 0.68) ≈ 1.18 ‰
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Deduction of the resorption deficit

From the theoretical BAC (blood alcohol level), a resorption deficit amounting to 15 percent of the alcohol quantity is deducted here. The resorption deficit is the proportion of alcohol that does not pass into the bloodstream when drunk and thus has no measurable BAC effect. This proportion, which is between 10 and 30 percent of the amount of alcohol consumed, depends on the alcohol content of the beverages and the filling state of the stomach. The reason for the absorption deficit is that part of the alcohol is exhaled, while another part is excreted unchanged in the urine or sweated out. Another portion is broken down by gastric alcohol hydrogenase (ADH) before it enters into the bloodstream. A full stomach increases the absorption deficit, as ethanol remains in the stomach longer and gastric ADH therefore has more time to break it down. The activity of gastric ADH varies in some people. In men, the enzyme activity is 70–80% higher than in women. Since the alcohol is not completely absorbed, the theoretical BAC (blood alcohol level), i.e., the calculation based on the amount consumed, can be subtracted from a value between 10 and 30 percent by volume. To be on the safer side, the above BAC Calculator only assumes a value of 15 percent (by volume).

Theoretical BAC minus resorption deficit (15 percent) for Ms Kirsch
1.18 ‰ - (1.18 × 15 / 100) ≈ 1.00 ‰
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Deduction of the hourly degradation value

Alcohol is broken down in the body primarily by the liver and gastric ADH. The hourly degradation value is considered to be between 0.1 and 0.2 per mille. In the forensic literature, a degradation rate of approx. 0.15 per mille is assumed, which was also taken into account here. Since Ms Kirsch consumed alcohol 3 hours ago, 0.45 per mille has already been reduced.

BAC minus degradation value for Ms Kirsch
1.00 ‰ - 3 × 0.15 ‰ = 0.55 ‰
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Final blood alcohol concentration of Ms Kirsch

Final BAC due to the amount drunk by Ms Kirsch
0.55 ‰
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When will Ms Kirsch be sober and fit to drive again?

With an hourly reduction of 0.15 per mille, Ms Kirsch will be sober again in just under 4 hours. This is illustrated in the results window of the BAC calculator by the chart on the alcohol reduction after the end of drinking.

Intended drinks in the BAC Calculator

The following drinks and their effects can be determined using the BAC Calculator: beer, alcopops, wine, sparkling wine, liqueurs, schnapps, and vodka.

Once you have drunk a glass or a bottle of these drinks, you need to convert that amount into the unit of measurement liter (or fluid ounce) and enter it into the calculator. A bottle of beer, for example, is usually equal to 0.33 liters, or 12 fluid ounces .

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Functionality of alcohol test with breathalysers

Digital breathalysers are the most common method of finding out how high the alcohol concentration is in a person's blood. This method can be used to check whether a person is still fit to drive under the influence of alcohol. This is relevant not only for novice drivers, but for all drivers and cyclists. About the devices: The alcohol content of the breathalyser is determined by electrochemical sensors; reliable breathalysers are accurate to +/- 0.05 per mille and the cost starts at 100.00 euros.

Source information

As source for the information in the 'BAC Calculator' category, we have used in particular:

Last update on January 12, 2023

The last changes in the 'BAC Calculator' category were implemented by Stefan Banse on January 12, 2023. The main changes were:

  • 12.01.2023: Publication of the BAC Calculator
  • Editorial revision of all texts in this category