CPU & energy

% CPU

How much processor time a process uses. Each core counts as 100%, so it can go above 100%.

What it is

Activity Monitor measures CPU per core: a process fully using one core shows 100%, and one using four cores shows 400%. A Mac with 10 cores can reach 1,000% in total.

The CPU tab's summary splits the whole Mac's use into System, User and Idle.

Should you worry?

High numbers during real work (exporting, compiling, gaming) are expected. Worry about apps that stay high while you aren't using them.

What you can do

Sort by % CPU and quit apps that are busy for no reason.
Update apps that regularly misbehave.

Guides

Processor

How to check CPU usage on a Mac (and what the numbers mean)

Four ways to check CPU usage on a Mac, from Activity Monitor to the Dock and Terminal, plus what “over 100%”, kernel_task and WindowServer really mean.

6 min read →

Performance

Why is my Mac running slow? 9 checks that actually help

A practical checklist for a slow Mac: find what’s using your processor and memory, free up storage, trim login items and know when a restart is the fix.

7 min read →