By default, Finder leaves the Size column blank for folders — macOS skips the calculation to keep navigation snappy. There are two native ways to force those sizes to show up.
Short answer: open the folder in List View, press Command + J, and turn on Calculate all sizes. For a pre-grouped view of the biggest files, use System Settings > General > Storage > Documents > Large Files.
Calculating sizes inside Finder
Turning this on per-folder (or globally) is the fastest way to find heavy directories without installing anything.
- open Finder and navigate to your Home folder
- switch to List View (press Command + 2)
- press Command + J to open View Options
- check Calculate all sizes
- (optional) click Use as Defaults so every Finder window gets this treatment
Wait a few seconds — the dashes in the Size column fill in with real numbers. Click the Size header to sort largest-first and the biggest folders rise to the top.
Using Storage Management's Large Files
macOS has a built-in browser that groups the heaviest single files regardless of folder depth.
- click the Apple menu in the top-left
- open System Settings > General > Storage
- click the ⓘ button next to Documents
- open the Large Files tab to see the biggest files anywhere on the drive
- open the File Browser tab for an interactive folder-by-folder size breakdown
This is the native replacement for the older "About This Mac > Storage > Manage" screen.
Better next routes
Native tools miss hidden caches and sandboxed containers. For that, read What is System Data on Mac?.
If you want a visual treemap instead of text columns, continue with Best Disk Space Analyzer for Mac (Free and Paid).