Choosing the right amount of storage for a Windows backup helps ensure you have enough space for your important files without buying a drive that is unnecessarily large.
The space you need depends on how much data you want to protect, including documents, photos, videos, downloads and other personal files. You should also allow room for future files and additional backups.
This guide shows you how to estimate the size of your Windows files, choose a suitable external drive and understand how much storage different backup methods may require.
Important: The size of your Windows user folder is a useful starting point for backing up personal files, but it may not include everything you need to protect. Installed applications, system files and other data may require additional space if you are planning a full system backup.
How to check how much space your files use
Click on “Users”
Select the User that you normally use, such as Your Name (eg fredsmith) or the one that has the most recent “Date Modified” … in this example it is called “Default” and will differ depending on how the computer was originally setup
Hovering over the user directory do a “right-click: and then click on “Properties”
This will show you the size of the user profile. In this example it is only 1.48 or 1.57 MB but it could be hundreds of MB or even many GB (Gigabytes)
How much external storage should you buy?
Once you know how much data you want to back up, choose an external drive with enough capacity for your current files and room for future growth.
For example, if the files you want to protect use 250 GB of storage, a 500 GB drive may provide enough room for a straightforward copy of those files. A 1 TB drive gives you more room for additional files and future backups.
Use these examples as a guide:
| Size of files to back up | Suggested drive capacity |
|---|---|
| Up to 250 GB | 500 GB |
| Around 500 GB | 1 TB |
| Around 1 TB | 2 TB |
| Around 2 TB | 4 TB |
These are practical estimates, not strict requirements. Allow extra space if you plan to keep multiple versions of your files, use File History, or back up additional computers.
Remember: A drive’s advertised capacity is not always the exact amount of usable space shown in Windows. Also, a simple file copy, File History backup and full system image can require different amounts of storage.
For instructions on copying your files to an external drive, see our guide to backing up Windows 10 or 11 to an external drive.
Frequently asked questions about backup storage
Is a 1 TB external drive enough to back up my computer?
A 1 TB drive may be sufficient if the files you want to back up fit comfortably within its usable capacity. Check the size of your files first and allow extra room for future growth or additional backups.
Should I buy an SSD or an external hard drive?
An external hard disk drive (HDD) is often a cost-effective choice for storing large amounts of backup data. A solid-state drive (SSD) is generally faster and has no moving parts, but it usually costs more for the same capacity. Either can be suitable for file backups.
Do I need a separate drive for each backup?
Not necessarily. You can store multiple backups on one drive if there is enough space and the backup methods support it. However, keeping another backup on a separate device or location provides additional protection if one drive fails, is lost or is damaged.
Does backing up to OneDrive use the same amount of storage?
The storage required depends on how much data you upload and what is included in your backup. OneDrive has its own storage allowance, so check your available cloud storage before uploading large amounts of data.
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Which Windows backup method should you use?
There are several ways to back up files in Windows. The best method depends on whether you want to protect selected personal files, maintain regular backups or keep a copy of your files online.
| Manual copying | How to Manually Back Up Windows to an External Drive |
| File History | How to Use File History to Back Up Windows |
| Backup and Restore | How to Use Backup and Restore in Windows 10 or 11 |
| OneDrive | How to Back Up Windows Files to OneDrive |
