Average Weight of Human Organs

Average weights of the major adult human organs, in grams, drawn from reference tables used in pathology. The liver is the heaviest internal organ at about 1,500 g, followed by the brain at 1,400 g and the lungs together at roughly 1,000 g.

The eight entries here add up to about 4,800 g — under five kilograms, or roughly six percent of a 75 kg adult. The liver and brain alone account for 60.4 percent of that total. At the other end of the scale, the thyroid weighs about 30 g, which means the liver is fifty times heavier than it. The heart and the kidneys are matched at about 300 g each, so the organ that pumps blood around the body weighs about the same as the pair of organs that filter it.

Weight is not a measure of importance, and this table is easy to misread as though it were. The thyroid is among the lightest organs listed and regulates metabolism throughout the body; the pancreas at 100 g controls blood sugar and produces digestive enzymes. What organ weight does track is the volume of blood an organ processes and the amount of tissue it needs to do its work — the liver handles a large share of the body's blood supply continuously, and it is built accordingly.

These are reference averages, not fixed values. Organ weights vary substantially with body size, sex, age and health: an adult's liver can range several hundred grams either side of the figure given here and still be entirely normal. Pathologists use tables like this as a starting point for comparison, not as a standard that any individual is expected to match.