How much do bacteria in a human body weigh?
AI-generated conceptual illustration of the human digestive tract with a magnified view of microbes. It is not an anatomical scan, exact representation, or proportional data graphic. Prompt: “Vertical 4:5 educational science illustration. A neutral translucent human torso silhouette with the digestive tract subtly highlighted, paired with an enlarged conceptual view of diverse tiny gut microbes around intestinal folds. Clean scientific museum illustration, calm blue and warm coral colors, accurate non-graphic anatomy, no text, no numbers, no scales, no measurement devices, no misleading size comparison. The magnification is illustrative and not to scale. Not a medical scan or data chart.” Generated 2026-10-29; no external source or documentary role.
The popular claim that microbes in a human body weigh 1–2 kilograms has no known original source and is likely an overestimate for most people. A detailed 2016 calculation estimated about 200 grams of wet bacterial mass for a reference 70-kilogram man; the dry bacterial mass in that model was about 50–100 grams. This is a model estimate, not a universal weighing of every person.
