--- title: "How many neurons are in the human brain? about 86 billion" description: "about 86 billion How the figure is estimated, how confident it is, and what makes the scale graspable." url: https://atoneplace.net/how-many/neurons-in-the-brain/ site: "At One Place" --- # How many neurons are in the human brain? **How many neurons are in the human brain?: about 86 billion** The cerebral cortex has about 16 billion neurons against the cerebellum's 69 billion, yet the cortex is where nearly all the interesting behaviour lives. Neuron count alone explains very little. The brain contains roughly 86 billion neurons and about 85 billion non-neuronal cells — a ratio of almost exactly one to one, not the ten glia per neuron that textbooks asserted for decades. That older claim, like the bacteria-to-cell ratio, was never based on a measurement. The distribution is counterintuitive: the cerebellum holds about 69 billion of the 86 billion neurons, roughly 80% of them, while the cerebral cortex — where thinking is supposed to happen — holds about 16 billion in a far larger volume. ## How the figure is arrived at The isotropic fractionator, and the method is the point. Instead of counting cells in thin slices and extrapolating — which fails because cell density varies enormously between regions — the tissue is dissolved into a homogeneous suspension of free nuclei. Stir it, take a sample, count nuclei under a microscope, and stain to distinguish neuronal from non-neuronal. Homogenising removes the sampling bias that made every earlier estimate unreliable. ## How confident it is - **Low estimate:** 80,000,000,000 - **High estimate:** 90,000,000,000 - **Spread:** 1.1× between the bounds ## Other the human body counts - [How many bones are in the human body?](https://atoneplace.net/how-many/bones-in-the-human-body/) — 206 in an adult — about 300 at birth - [How many cells are in the human body?](https://atoneplace.net/how-many/cells-in-the-human-body/) — about 30 trillion human cells, plus 38 trillion bacteria - [How many muscles are in the human body?](https://atoneplace.net/how-many/muscles-in-the-human-body/) — about 600 skeletal muscles - [How many hairs are on your head?](https://atoneplace.net/how-many/hairs-on-your-head/) — about 100,000 - [How many taste buds do you have?](https://atoneplace.net/how-many/taste-buds/) — about 2,000 to 8,000 - [How long are all your blood vessels?](https://atoneplace.net/how-many/blood-vessels-length/) — commonly quoted as 100,000 km — but probably closer to 20,000 - [How many base pairs are in human DNA?](https://atoneplace.net/how-many/dna-base-pairs/) — about 3.1 billion per copy — 6.2 billion in most cells ## Common questions ### How many neurons are in the human brain? about 86 billion ### How is that estimated? The isotropic fractionator, and the method is the point. Instead of counting cells in thin slices and extrapolating — which fails because cell density varies enormously between regions — the tissue is dissolved into a homogeneous suspension of free nuclei. Stir it, take a sample, count nuclei under a microscope, and stain to distinguish neuronal from non-neuronal. Homogenising removes the sampling bias that made every earlier estimate unreliable. ## Related pages - [How many bones are in the human body?](https://atoneplace.net/how-many/bones-in-the-human-body/) - [How many cells are in the human body?](https://atoneplace.net/how-many/cells-in-the-human-body/) - [How many muscles are in the human body?](https://atoneplace.net/how-many/muscles-in-the-human-body/) - [How many hairs are on your head?](https://atoneplace.net/how-many/hairs-on-your-head/) - [How many taste buds do you have?](https://atoneplace.net/how-many/taste-buds/) - [How long are all your blood vessels?](https://atoneplace.net/how-many/blood-vessels-length/) - [How many base pairs are in human DNA?](https://atoneplace.net/how-many/dna-base-pairs/) - [How many people are there in the world?](https://atoneplace.net/how-many/people-alive-right-now/) - [How many stars are there in the universe?](https://atoneplace.net/how-many/stars-in-the-universe/) - [How many countries are there in the world?](https://atoneplace.net/how-many/countries/) - [How many grains of sand are there on Earth?](https://atoneplace.net/how-many/grains-of-sand-on-earth/) - [How many ants are there in the world?](https://atoneplace.net/how-many/ants-on-earth/) - [How many trees are there in the world?](https://atoneplace.net/how-many/trees-on-earth/) ## Sources - Typical range compiled from manufacturer specifications — At One Place (/about/)