Skip to main content

The estimation of blood alcohol concentration

Widmark revisited


Expert witnesses and others involved in toxicology are frequently asked to perform retrograde extrapolation of blood alcohol concentration (BAC) or to estimate BAC based on a proposed drinking scenario. Although many individuals are reluctant to perform these calculations and some jurisdictions expressly prohibit them, a significant number of practitioners routinely estimate BAC based on this type of calculation, using as a basis the fundamental work of Widmark. Although improvements to the Widmark formula and other data pertaining to the pharmacology of alcohol have been published, these improvements are frequently ignored when estimating BAC. This article summarizes five published models for the estimation of BAC and proposes a sixth model that incorporates recent data on the rate of absorption of alcohol from the GI tract into the existing five models. The five improved models can be computerized and used to construct comparative snapshots of the BACs calculated by the different algorithms. This will allow practitioners to provide a more balanced picture of the variability in BAC calculations.

This is a preview of subscription content, access via your institution.


  1. Widmark EMP. Die theoretischen Grundlagen und the praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung. Berlin: Urban & Schwarzenberg, 1932.

    Google Scholar 

  2. Uemura K, Fujimiya T, Ohbora Y, Yashuhara M, Yoshida K. Individual differences in the kinetics of alcohol absorption and elimination: A human study. Forensic Sci Med Pathol, 2005;1:24–27.

    Google Scholar 

  3. Watson PE, Watson ID, Batt RD. Prediction of blood alcohol concentrations in human subjects: updating the Widmark equation. J Stud Alcohol 1989;42:547–556.

    Google Scholar 

  4. Forrest ARW. The estimation of Widmark’s factor. J For Sci Soc 1986;26:249–252.

    CAS  Google Scholar 

  5. Seidl S, Jensen U, Alt A. The calculation of blood ethanol concentrations in males and females. Int J Legal Med 2000;114:71–77.

    PubMed  Article  CAS  Google Scholar 

  6. Ulrich L, Cramer Y, Zink P. Relevance of individual parameters in the calculation of blood alcohol levels in relation to the volume of intake. Blutalkohol 1987;24:192–198.

    PubMed  CAS  Google Scholar 

  7. Altman PL, Dittmer DS, eds. Blood and Other Body Fluids, Washington DC: Federation of American Societies for Experimental Biology, 1961.

    Google Scholar 

  8. Durnin JVGA, Womersly J.. Body fat assessed from total body density and its estimation from skin fold thickness. Br J Nutr 1974;32:77–97.

    PubMed  Article  CAS  Google Scholar 

  9. Dubowski KM. Human pharmacokinetics of ethanol: I. Peak blood concentrations and elimination in male and female subjects. Alcohol Tech Rep 5, 1976:55–63.

    Google Scholar 

  10. Shajani NK, Dinn HM. Blood alcohol concentrations reached in human subjects after consumption of alcoholic beverages in a social setting. Can Soc Forensic Sci J 1985;18:38–48.

    CAS  Google Scholar 

  11. Tam TW, Yang CT, Fung WK, Mok VK. Alcohol metabolism of local Chinese in Hong Kong: a statistical determination on the effects of various physiological factors. Forensic Sci Int 2006;156:95–101.

    PubMed  Article  CAS  Google Scholar 

  12. Zuba D, Piekoszewski W. Uncertainty in Theoretical Calculations of Alcohol Concentration. Presented at the 17th International Conference on Alcohol, Drugs and Traffic Safety (ICADTS). Glasgow, UK, 2004, Available at:

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Douglas Posey.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Posey, D., Mozayani, A. The estimation of blood alcohol concentration. Forens Sci Med Pathol 3, 33–39 (2007).

Download citation

  • Accepted:

  • Issue Date:

  • DOI:

Key Words

  • Forensic toxicology
  • Widmark
  • extrapolation
  • alcohol
  • ethanol
  • blood