Revised Estimates for the Number of Human and Bacteria Cells in the Body

PLoS Biol. 2016 Aug 19;14(8):e1002533. doi: 10.1371/journal.pbio.1002533. eCollection 2016 Aug.


Reported values in the literature on the number of cells in the body differ by orders of magnitude and are very seldom supported by any measurements or calculations. Here, we integrate the most up-to-date information on the number of human and bacterial cells in the body. We estimate the total number of bacteria in the 70 kg "reference man" to be 3.8·1013. For human cells, we identify the dominant role of the hematopoietic lineage to the total count (≈90%) and revise past estimates to 3.0·1013 human cells. Our analysis also updates the widely-cited 10:1 ratio, showing that the number of bacteria in the body is actually of the same order as the number of human cells, and their total mass is about 0.2 kg.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bacteria / cytology
  • Bacteria / growth & development*
  • Bacterial Load*
  • Body Weights and Measures
  • Cell Count*
  • Humans
  • Male
  • Microbiota*
  • Organ Specificity

Grants and funding

This work was funded by the European Research Council (Project NOVCARBFIX 646827,; Dana and Yossie Hollander; Helmsley Charitable Foundation; The Larson Charitable Foundation; The Estate of David Arthur Barton; The Anthony Stalbow Charitable Trust, and Stella Gelerman, Canada. RM is the Charles and Louise Gartner professional chair and an EMBO young investigator program member. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.