Check fan speed on a Mac

Short answer

On Apple Silicon Macs, macOS has no built-in command or window that shows fan speed. On Intel Macs, sudo powermetrics --samplers smc includes it. Otherwise you need an app that reads the System Management Controller (SMC). MacBook Air models have no fan at all.

What you can check

Does powermetrics have the SMC sampler here?

powermetrics -h | grep -c smc

On an M4 Max MacBook Pro this prints 0: the sampler is not offered. The powermetrics man page describes the smc sampler as reporting fan speed and temperature sensors "on supported platforms", which in practice means Intel Macs, where it needs sudo:

sudo powermetrics --samplers smc -n 1

The IORegistry does not have it either

ioreg -l | grep -ic '"fan'

Whether heat is a problem at all

pmset -g therm

Note: No thermal warning level has been recorded
Note: No performance warning level has been recorded

Why you might care

Fans spin up because something is producing heat. If they are loud, the useful question is which process is causing it: top -l 2 -n 10 -o cpu -stats pid,command,cpu answers that. A fan that runs fast with no load, or never runs while the Mac is hot, is worth a visit to Apple Diagnostics or a repair shop.

The easier way: GaugeMon

GaugeMon reads fan speed from the SMC, read-only and without sudo, on both Apple Silicon and Intel Macs that have fans. Show it in the menu bar next to temperature; on a MacBook Air the Fans gauge is simply hidden.

Download GaugeMon free trial Learn more