Disk Usage Calculator
Estimate total disk usage from a file count and average file size, and see what percentage of total disk that consumes.
Inputs
Total number of files
Estimated Used Space
24.414GB
Percent of Total Disk Used
24.41%
Estimated Used Space
25,000.00MB
Estimated Free Space
75.586GB
Status
Healthy
Step by step
Values used
File Count = 100,000; Average File Size = 256 KB; Total Disk Size = 100 GB
Used space
used = file_count × avg_file_size
Usage percentage
used% = (used / total_disk) × 100
Estimated Used Space
= 24.414 GB
Percent of Total Disk Used
= 24.41
Estimated Used Space
= 25,000.00 MB
Estimated Free Space
= 75.586 GB
Status
= Healthy
How it works
Total used space is estimated by multiplying the number of files by their average size, mirroring the rough math behind the `du` command's summary output. Comparing that estimate to the total disk capacity yields a usage percentage, which is flagged as a warning at 80% and critical at 95% — the same thresholds most Linux monitoring tools default to.
Formulas
Used space
used = file_count × avg_file_size
- n
- file count
- \bar{s}
- average file size
Usage percentage
used% = (used / total_disk) × 100
- U
- used space
- T
- total disk capacity
Frequently Asked Questions
Why is this only an estimate?
Real filesystems round each file up to a multiple of the block size and also store metadata (inodes, directory entries), so actual usage from `du` or `df` is typically higher than file_count × average_size, especially with many small files.
What disk usage percentage should trigger an alert?
Most monitoring setups warn at 80% and escalate to critical at 90-95%, leaving headroom for logs, temp files and snapshots before the filesystem fills completely.
How is this different from the Filesystem Utilization Calculator?
This calculator projects usage from file count and average size — useful for capacity planning before files exist. The Filesystem Utilization Calculator works from actual used/total block counts reported by `df`.