How Many Muscles In the Human Body? A slightly tongue-in-cheek tally of our many muscles

There are about 700 named skeletal muscles in the human body, including roughly 400 that no one cares about except specialists. There is just one important cardiac muscle. And there are literally countless smooth muscles (which do the work of the autonomic nervous system, mostly squeezing and squishing stuff in tubes).

But it depends on how you count. So how many muscles really?

It’s surprisingly hard to tell. You wouldn’t think the total number would be ambiguous, but it’s difficult to know what to include and exclude, and anatomists don’t always agree. Some muscle tissue really can’t be separated into countable muscles. And, believe it or not, the science of anatomy is still advancing. No, entirely new muscles aren’t being discovered — but novel variations in individual muscle anatomy are found more or less constantly,1 and supernumerary muscles — extra muscles — are not unusual.2 Many muscles, like the four-part quadriceps, are normally split into different parts that may or may not traditionally count as separate muscles3 — but then some people’s muscles are more divided than others. It makes a firm count just about impossible.

ZygoteBody.com is a free online, 3D model of the human body. Layers of tissue can be removed or made transparent and zoomed. Most anatomy is labelled and searchable.

There are only about 200 to 300 muscles that anyone, even a massage therapist, might actually be interested in knowing about. When most people ask how many muscles are in the human body, they mean the serious bone-movers — muscles that do real work, muscles like pecs, delts, lats, traps, glutes, biceps and triceps, hams and quads, and let’s not forget the cloits and dloits!4

There are maybe another hundred muscles if you include the fiddly little muscles of the hands and feet, and the major face muscles. In school, I had to learn the Latin for all them!

No, really, how many muscles are there?

All right, all right — if you really must know, there are just shy of 700 named skeletal muscles.5

But that’s including about 400 muscles that, mostly, no one cares about except specialists. I am aware of a few that have clinical importance to a massage therapist, but I’m mostly just barely aware of their existence — like the smaller facial muscles, like the mess of little muscles around and under the tongue and around the voice box, like the muscles around the eyeball, or the crazy trampoline of muscles on the pelvic floor.

But believe it or not, although that’s all of the muscles you can count, that’s still not all of the muscle — not even close.

Cartoon by Loren Fishman, HumoresqueCartoons.com

There’s more? Oh hell yes.

Muscles comes in three types:

skeletal, which moves us cardiac, which moves our blood smooth, which moves our bowels … and a lot more

If we include smooth muscle in our census, the job becomes truly impossible. Smooth muscle is the muscle of organs, the muscle that does the work of the autonomic nervous system, squeezing and squishing stuff in tubes mostly, but also raising hairs, focusing eyes, raising hairs,6 and pushing out babies.7 Smooth muscle blends with other smooth muscle, and exists at every scale from microscopic. You have single cells of smooth muscle wrapped around capillaries, and you have organs like your stomach that are wrapped completely in three thick layers of smooth muscle. It’s impossible to say where one smooth muscle stops and the next begins. Perhaps that’s why they call it smooth.8

At the other counting extreme, of course there’s that singular cardiac muscle: a category of one. Unless you’re a Klingon or a Time Lord, you have only one cardiac muscle, but hopefully it’s a big one.

Fun Fact: The iris of the eye consists of two muscles, which can contract to just 10% of its length, with a “ruffled” structure that folds up like an accordion (the radial contraction folds of Schwalbe, which make up the pupillary ruff.)

Doing the muscle math

This is how I calculate it. We have …

~100 muscles that might get discussed in a gym (and of course only 20% of those get 80% of the shop talk)

~200 more muscles that are more obscure, but any self-respecting massage therapist should still know about them (or at least memorized them in school 12 years ago)

roughly 400 more muscles that are really danged obscure, but various specialists know about them, and a handful are of special interest

several million hair-raising muscles

several billion smooth muscles cells blended together

exactly 1 heart muscle

So I’m going to go with a grand total of approximately 50,100,000,701 muscles, accurate to within 99%.

About Paul Ingraham I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter.

Related Reading

This article is part of the Biological Literacy series — fun explorations of how the human body works, what I think of as “owner’s manual stuff.” Here are ten of the most popular articles on this theme:

Notes