Calculate disk used and free space percentages, convert storage units, and find how much to clean up or add to reach a target capacity.
Disk Usage Formulas
The calculator supports current utilization, cleanup and capacity expansion. Reserve is physically free space unavailable to users; utilization uses total physical capacity.
Cleanup to a maximum used percentage
Capacity expansion
Drive status
- TargetFraction — target used percentage divided by100
- Reserve — physically free space unavailable to users
- Available — physical free space minus reserve
- Capacity — total drive size
- Used — space already occupied
Decimal MB, GB and TB mean10⁶,10⁹ and10¹² bytes; binary MiB, GiB and TiB mean2²⁰,2³⁰ and2⁴⁰ bytes. Unit changes convert entered quantities.1TB is about931.32GiB before filesystem effects. Reserve stays fixed in the cleanup/expansion scenarios. No automatic10% buffer is applied.
Illustrative File Sizes and Capacity Planning
These file-size ranges are illustrative; compression, format and content can change actual sizes. They are not calculator defaults. Utilization alone does not diagnose drive health.
| File type | Typical size |
|---|---|
| Word document or short PDF | 0.1 to 1 MB |
| MP3 song (3 min) | 3 to 5 MB |
| Phone photo (JPEG) | 2 to 5 MB |
| RAW photo (DSLR/mirrorless) | 20 to 50 MB |
| 1 minute, 1080p video | ~130 MB |
| 1 minute, 4K video | ~375 MB |
| PC game install | 30 to 150 GB |
| Disk image / VM | 5 to 100 GB |
| Used | Status | What to do |
|---|---|---|
| Below 80% | Below an illustrative planning target | Check workload, update requirements and manufacturer guidance. |
| 80 to 90% | Reduced free-space margin | Review growth and choose a suitable cleanup or expansion target. |
| Above 90% | Small remaining margin | Check actual workload needs; this is not a health or failure threshold. |
Worked Example
A drive has1000GB total capacity and850GB used. Choose an80% maximum utilization target.
Cleanup = max(0,850 −0.80 ×1000) =50GB.
Alternatively, required total =850/0.80 =1062.5GB; addition =62.5GB.
These are alternative plans: remove50GB or add62.5GB while retaining the current used data. Neither action is performed by the calculator.
FAQ
Why might a1TB drive show about931GiB?
1TB is10¹² bytes;1TiB is2⁴⁰ bytes. A display using binary units may show about931.32GiB for1TB before formatting, reserved space and other effects. Some systems use a GB label for a binary quantity.
How does the reserve input work?
Reserve subtracts an entered amount from physically free space to estimate user-available capacity. Blank means zero. Do not double-count reserve already included in used space or capacity excluded from the entered total.
Is80% a universal SSD health threshold?
No. Headroom and over-provisioning can affect performance, but requirements depend on the device and workload. Consult its documentation; the calculator uses your chosen target and does not assess SSD health.
