Storage Capacity Planner
Check how many files fit after allowing for system space and a free-space reserve.
iTechVora Tools
Storage Capacity Planner
Check how many files fit after allowing for system space and a free-space reserve.
Free · No signup · Calculations run in your browser
Ready to calculate
How to use
Enter values from your device specifications or measurements, then select Calculate. Defaults are editable examples. Copy result saves a text summary; Copy link shares your inputs. Reset restores the example.
Methodology
Available GB = maximum of zero and (capacity GB × (1 − reserve / 100) − system GB). Files = floor(available GB × 1,000 / average file MB). GiB = GB × 1,000,000,000 / 1,073,741,824.
Worked example
256 GB, 30 GB already used, a 10% reserve and 5 MB files leaves 200.4 GB, enough for 40,080 files.
Limits and sources
The reserve is a user preference, not a manufacturer requirement. Enter existing usage in decimal GB. Compression, filesystem overhead and actual file-size variation are excluded.
Background reference: Official guidance. The source supports the background concepts; results use the formula above.
FAQ
Why does a drive show fewer GB than advertised?
Decimal GB and binary GiB count the same bytes differently. Formatting and existing files can reduce available space further.
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Methodology version 1 · Updated October 11, 2026.