The fastest way to check disk space on Windows, Mac, and Linux

On Windows, right-click your hard drive in File Explorer, select Properties, and look at the pie chart — it shows used space in blue and free space in white. On Mac, click the Apple menu, choose About This Mac, then Storage — you'll see a colored bar breaking down what's using your drive. On Linux, open a terminal and type df -h to see all drives and how much space each has left. All three methods take under 30 seconds and show you the same information: total capacity, used space, and free space remaining.

The reason to check matters. If your drive is nearly full — typically above 85 to 90 percent used — your computer slows down because the operating system needs free space to write temporary files, run updates, and handle everyday tasks. Checking regularly helps you catch the problem before your machine starts freezing or refusing to install updates.

Key Takeaways

  • Windows shows disk space in File Explorer Properties; Mac shows it in About This Mac under Storage; Linux users open a terminal and type df -h.
  • A full drive (above 85 to 90 percent used) causes slowdowns because your operating system needs free space for temporary files and updates.
  • You can see which folders are taking up the most space by using built-in tools: Disk Usage Analyzer on Linux, Storage Sense on Windows, or About This Mac on Mac.
  • External drives and cloud storage show up in the same places as internal drives, so you can check all your storage from one location.

Checking disk space on Windows

Open File Explorer and locate your hard drive — usually labeled C: or Local Disk (C:) in the left sidebar. Right-click it and select Properties. A window opens showing a pie chart at the top: the blue section is used space, the white section is free space. Below the chart, you'll see exact numbers: "Used" and "Free" in gigabytes or terabytes. This is the quickest way to get a single number for how much room you have left.

If you want to see what's eating up your space, Windows 10 and 11 include a built-in tool called Storage Sense. Go to Settings > System > Storage. The top bar shows your overall usage, and below it you'll see categories — Documents, Pictures, Videos, Apps, and so on — with the size of each. Click any category to drill down further. This takes longer than the Properties method but tells you where to focus if you need to free up space.

Checking disk space on Mac

Click the Apple menu in the top-left corner and select About This Mac. A window opens; click the Storage tab. You'll see a horizontal bar showing your drive broken into colored sections: red for documents and backups, orange for photos and videos, yellow for audio, blue for apps, and gray for system files. The total capacity appears on the right side of the bar, and hovering over each color shows the exact size of that category.

The Storage tab also shows how much free space you have at the bottom. If you need more detail, click Manage to see recommendations for freeing space — Mac will suggest deleting old files, emptying the trash, or removing large old apps. This is the Mac equivalent of Windows' Storage Sense and works the same way: it categorizes what's on your drive so you can decide what to delete.

Checking disk space on Linux

Open a terminal window and type df -h (the -h flag means "human-readable," so sizes show in gigabytes instead of raw bytes). Press Enter. You'll see a table with columns for Filesystem, Size, Used, Avail (available), and Use%. Each row is a drive or partition. Look at the "Avail" column to see free space and the "Use%" column to see how full each drive is as a percentage.

If you want to see which folders are taking up the most space, type du -sh * in your home directory (or any folder you want to check). This shows the total size of each folder and file in that location, sorted from smallest to largest. Combine it with sort -h to sort by size: du -sh * | sort -h. These commands take a few seconds to run on large folders but give you a clear picture of what's using your drive.

Understanding the numbers: what "full" actually means

Your drive doesn't need to hit 100 percent full to cause problems. Most operating systems start to slow down noticeably around 85 to 90 percent capacity. At that point, the system has less than 10 to 15 percent free space to work with, and it needs that buffer for temporary files, cache, virtual memory, and system updates. If you hit 95 percent or higher, you may see error messages, failed updates, or the system refusing to write new files at all.

The exact threshold depends on your drive size. A 500 GB drive at 90 percent full has 50 GB free, which is usually enough. A 256 GB drive at 90 percent full has only 25 GB free, which is tighter. If you're consistently above 85 percent, it's time to delete files, move them to external storage, or upgrade your drive.

Checking space on external drives and USB sticks

External drives and USB sticks show up in the same places as your main drive. On Windows, they appear in File Explorer with their own letter (D:, E:, and so on). Right-click and select Properties to see their space the same way. On Mac, they show up in the Finder sidebar and in About This Mac under Storage. On Linux, they appear in the df -h output with their own mount point, usually something like /media/username/drivename.

The process is identical to checking your main drive — the only difference is which drive you're looking at. This is useful if you're thinking about moving files to an external drive to free up space on your main drive; you can check both before you start moving anything.

What to do if your drive is almost full

If you're above 85 percent capacity, start by identifying what's taking up space. Use Storage Sense on Windows, the Storage tab on Mac, or du -sh on Linux to see which folders or file types are the largest. Common culprits are old video files, photo libraries, downloads folders that never get cleaned out, and application caches.

Your options are to delete files you don't need, move large files to external storage or cloud storage, or uninstall apps you're not using. Don't delete system files or anything in your Program Files (Windows) or Applications (Mac) folder unless you're sure what you're doing. If you're unsure what something is, search for it online before deleting it. Once you've freed up space, aim to keep your drive below 80 percent full to avoid slowdowns.

Frequently Asked Questions

Why does my drive show less free space than I expected?

System files, hidden files, and application caches take up more space than most people realize. Windows system files alone can use 20 to 30 GB. Temporary files, browser caches, and old backups add more. Use your operating system's built-in tool (Storage Sense, Storage tab, or du) to see exactly what's using the space, then decide what to delete.

Is it safe to delete files from my Downloads folder?

Yes, if you've already moved or installed what you downloaded. The Downloads folder is meant to be temporary. Old installers, documents you've already opened, and files you've moved elsewhere are safe to delete. Just make sure you don't need them first — if you're unsure, move them to an external drive instead of deleting them.

Can I check disk space on my phone or tablet?

Yes. On iPhone and iPad, go to Settings > General > iPhone Storage (or iPad Storage). On Android, go to Settings > Storage. Both show total capacity, used space, and a breakdown by app and file type. The process is the same as on computers — if you're above 85 percent full, delete apps or files you don't need.

What's the difference between GB and TB?

One terabyte (TB) equals 1,000 gigabytes (GB). Older drives are usually measured in GB (256 GB, 512 GB, 1 TB). Newer or larger drives are measured in TB (2 TB, 4 TB). When you check your disk space, your operating system automatically shows the right unit — you don't need to convert between them yourself.