---
id: mac-storage-basics.how-big-should-a-time-machine-drive-be
url: https://storagestudio.us/faq/mac-storage-basics/how-big-should-a-time-machine-drive-be
category: "Mac storage basics"
subcategory: "Time Machine basics"
question: "How big should my Time Machine backup drive be?"
alt_questions:
  - "time machine drive size"
  - "how much space for time machine"
  - "what size external drive for backup mac"
  - "time machine disk capacity"
  - "time machine needs bigger drive"
short_answer: "Roughly twice the data you back up, so it can keep a useful history. A smaller drive still works; Time Machine deletes the oldest backups when it's full."
tags: ["time machine", "backup", "drive size"]
related: ["https://storagestudio.us/faq/mac-storage-basics/what-does-time-machine-delete-when-the-drive-is-full", "https://storagestudio.us/faq/mac-storage-basics/how-do-i-exclude-folders-from-time-machine"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# How big should my Time Machine backup drive be?

A common rule of thumb is at least twice the amount of data you're backing up, so Time Machine can keep a useful history of older versions. If you back up 500 GB, a 1–2 TB drive gives room for months of history.

When it fills, Time Machine deletes the oldest backups automatically to make room, so a small drive still works — it just keeps less history.