---
id: mac-storage-basics.why-does-get-info-show-size-and-on-disk
url: https://storagestudio.us/faq/mac-storage-basics/why-does-get-info-show-size-and-on-disk
category: "Mac storage basics"
subcategory: "Finding big files, Downloads and the Trash"
question: "Why does Get Info show two sizes — the size and \"on disk\"?"
alt_questions:
  - "get info size vs on disk"
  - "bytes vs on disk mac"
  - "why is on disk bigger"
  - "size on disk smaller than size mac"
  - "finder size explained"
short_answer: "Size is the content total; on disk is the space actually used. They differ because of block allocation, compression, sparse files and online-only cloud files."
tags: ["get info", "finder", "file size"]
related: ["https://storagestudio.us/faq/mac-storage-basics/why-do-two-copies-of-a-file-not-use-double-the-space", "https://storagestudio.us/faq/mac-storage-basics/why-is-a-folder-a-different-size-on-another-drive"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# Why does Get Info show two sizes — the size and "on disk"?

The first number is the total of the file's contents; **on disk** is the space it actually occupies. They differ because storage is allocated in blocks (many small files take more on disk than their contents), some files are compressed by the file system, sparse files reserve less than their size, and online-only cloud files take almost nothing on disk.

For freeing space, the on-disk figure is the one that matters.