The body generally contains slightly more bacterial cells than human cells, but the often-repeated estimate of 10 bacterial cells for every human cell is outdated. Current estimates place the average ratio near 1.3 to 1, with substantial variation.
True
The human body has more bacterial cells than human cells.
Scientists bust myth that our bodies have more bacteria than human cells | Nature
Source: nature.com
At a glance
Verified August 28, 2026Key Evidence
A 2016 scientific analysis estimated approximately 1.3 bacterial cells per human cell in a typical adult, rather than the traditionally cited 10-to-1 ratio.
Bacterial and human cell totals are estimates that vary with individual biology, gut contents, and the definitions used for each cell category.
Several sources repeat the older 10-to-1 figure, but later scientific and explanatory sources describe the ratio as close to 1-to-1, with bacteria slightly more numerous.
The reporting
What the Evidence Shows
A 2016 analysis estimated that a typical adult carries about 1.3 bacterial cells for every human cell, supporting the claim in its narrow form. The study revised the older “10-to-1” estimate by using more detailed calculations of bacterial populations and human cells, particularly by accounting for the large number of human cells in blood.nature.comnature.comScientists bust myth that our bodies have more bacteria than human cells
sciencedirect.comsciencedirect.comAre We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host...+1 more
The comparison is an estimate, not a fixed biological constant. Bacterial numbers vary among individuals and can change substantially with factors such as gut contents and defecation. The result also depends on what is counted, including whether the comparison concerns bacterial cells alone or all microbes, and whether all human cells or only nucleated cells are included.microbiomeinstitute.orgmicrobiomeinstitute.orgHow many bacteria vs human cells are in the body?
sorbonne-universite.frsorbonne-universite.frIs it true that there are more microbes than cells in the human body? | Sorbonne...+2 more
Some educational and popular-science sources still repeat the older claim that bacteria outnumber human cells by 10 to 1, while others summarize the broader idea that microbial cells outnumber human cells without stating the revised ratio. Those accounts reflect the historical estimate or a simplified presentation, rather than disproving the more recent near-equivalence estimate.voanews.comvoanews.comWe're Only About 43% Human, Study Shows
ibiology.orgibiology.orgThe Human Microbiome: Are We More Microbial than Human? • iBiology+3 more
Thus, the statement is accurate as a broad comparison: bacterial cells are estimated to be more numerous than human cells in a typical body. The important qualification is that the difference is probably modest, not tenfold, and the exact ratio varies with the person and the counting method.
Primary trail
Verified Sources10
Open source