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06 Numbers and Powers

Available Disk Space: How to Check and Free Up Storage

Card No. 06·67912 · Updated · Standard formula, shown below

Free space 150.00 GB
Free space
30.0 %
Result
Total capacity
500 GB
You entered
Used space
350 GB
You entered
You enter
Total capacity, Used space
You get
Free space, Free space
Rounding
2 dp · 1 dp

Available disk space is the amount of unused storage capacity on a hard drive, SSD, or other storage device. To check it, open File Explorer (Windows) or Finder (Mac) and look at the drive’s properties or “Get Info”—you’ll see the free space in gigabytes (GB) or terabytes (TB). This article explains how to check available space on all major operating systems, what factors reduce it, and how to free up storage safely.

Formula

Free space = Total capacity − Used space. In symbols: F = T − U, where:

  • F = free space (GB or TB)
  • T = total capacity (GB or TB)
  • U = used space (GB or TB)

All units must match—if T is in GB, U must be in GB. The percentage free is (F / T) × 100.

Worked Example

Using the default values: a 500 GB drive with 350 GB used.

  1. Free space = 500 − 350 = 150 GB
  2. Free percentage = (150 / 500) × 100 = 30.0%

The calculator returns 150.00 GB and 30.0%, matching the formula.

How to Check Available Disk Space on Windows

Windows offers several ways to see free space:

  • File Explorer: Open “This PC” (or “My Computer”). Each drive shows a bar and the amount free under it.
  • Drive Properties: Right-click a drive → Properties → General tab. Shows used and free space, plus a capacity bar.
  • Settings: Settings → System → Storage. Shows a breakdown by category (apps, documents, temporary files).
  • Command line: Open Command Prompt and type wmic logicaldisk get size,freespace,caption to list all drives with their free space in bytes.

How to Check on macOS

On a Mac, the methods are:

  • Finder: Click the drive icon on the desktop or in Finder’s sidebar, then press Command+I (Get Info). The info window shows Capacity, Available, and Used.
  • About This Mac: Apple menu → About This Mac → Storage tab. Shows a color-coded bar of used space by category.
  • Disk Utility: Applications → Utilities → Disk Utility. Select a volume to see capacity and free space.
  • Terminal: Type df -h to see all mounted volumes with human-readable sizes.

How to Check on Linux

Linux users commonly use:

  • Files (GNOME): Open the file manager and look at the bottom of the sidebar—it shows free space for each mounted drive.
  • df command: In a terminal, df -h shows all mounted filesystems with sizes and free space.
  • Disks utility: GNOME Disks shows a graphical representation of each drive and its free space.
  • GUI system monitor: Many desktop environments include a system monitor that shows storage usage.

Why Is My Available Disk Space Less Than Advertised?

Manufacturers advertise hard drives using decimal units (1 GB = 1,000,000,000 bytes), while operating systems use binary units (1 GiB = 1,073,741,824 bytes). This means a “500 GB” drive shows as about 465 GB in Windows. Additionally, the file system itself (NTFS, APFS, ext4) uses some space for metadata, and hidden system files (like the Windows pagefile and hibernation file) consume several GB. These factors are normal and don’t indicate a defect.

Common Causes of Low Disk Space

Several things eat up storage without you noticing:

  • System files: Windows updates, macOS snapshots, and Linux package caches can accumulate.
  • Temporary files: Browser caches, installer leftovers, and app temp data.
  • Large media: Videos, photos, and music collections, especially in high resolution.
  • Applications: Installed programs, especially games and design software, can be several GB each.
  • Downloads folder: Old installers and files you forgot about.
  • Recycle Bin/Trash: Deleted files still occupy space until the bin is emptied.

How to Free Up Disk Space Safely

Before deleting anything, ensure you have backups of important files. Then try these methods:

  1. Use built-in cleanup tools: Windows Disk Cleanup (cleanmgr) or Storage Sense; macOS Storage Management; Linux’s BleachBit (if installed).
  2. Empty the Recycle Bin/Trash.
  3. Uninstall apps you don’t use. On Windows: Settings → Apps; macOS: drag to Trash or use an uninstaller.
  4. Move large files to an external drive or cloud storage. Videos and backups are prime candidates.
  5. Clear browser caches. Each browser has a settings option to clear cached files.
  6. Delete old system restore points (Windows). Keep the most recent one.

Frequently Asked Questions

How much free disk space do I need?

For normal use, keeping at least 10-15% of your drive free is recommended. This allows room for temporary files, system updates, and helps maintain performance. For SSDs, some controllers use free space for wear leveling and garbage collection, so a little extra headroom is beneficial.

Why does my USB drive show less space than its label?

Same reason as internal drives: the drive uses decimal units, and the file system (FAT32, exFAT, NTFS) takes some space for its own structure. A 64 GB USB drive typically shows about 58-59 GB usable.

Is it safe to delete files from the Windows.old folder?

Yes, if you don’t need to roll back to a previous Windows version. It can be removed via Disk Cleanup (select “Clean up system files” and check “Previous Windows installation(s)”). This can free up 10-20 GB or more.

What is the difference between free space and available space?

They are essentially the same. Some systems report “available” after accounting for system reservations (like Windows’ System Restore or macOS’s local Time Machine snapshots). The difference is usually small.

Can I increase available disk space without deleting files?

Yes, by compressing files (NTFS compression on Windows, APFS compression on macOS), moving files to another drive, or using cloud storage. However, compression can slow performance on older systems.

How do I check disk space on my phone?

On Android: Settings → Storage. On iPhone: Settings → General → iPhone Storage. Both show a breakdown and suggest ways to free space.

Related

Formula used
in t | Total capacity | GB | 500 | 1 | 100000
in u | Used space | GB | 350 | 0 | 100000
out free | Free space | GB | t - u | 2
out free_pct | Free space | % | (t - u) / t * 100 | 1

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.

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