Filesystem Inode Requirement Calculator

Work out filesystem inode requirement instantly with clear inputs, formula shown and shareable results.

About Filesystem Inode Requirement Calculator

ext4 allocates inodes at format time, one per bytes-per-inode of capacity, and the count cannot be increased afterwards. The default of 16 KB per inode suits general use but exhausts long before the disk fills when files average a few kilobytes — the classic no space left on device error with gigabytes free. XFS allocates inodes dynamically and avoids the problem.

Formula

Inode budget

inodes = filesystem bytes / bytes-per-inode; files expected = filesystem bytes / average file size; table size = inodes x inode size

Worked example

With the default values below, Filesystem Inode Requirement Calculator returns Inodes the filesystem will have of 30,517,578. Change any input above and every figure here is recalculated in your browser.

Inputs used

Filesystem sizeminimum 0.001 GB: 500 GB
Average file sizeminimum 0.1 KB: 64 KB
Bytes per inode settingminimum 1,024 bytes: 16,384 bytes
Inode structure sizeaccepts 128–1,024 bytes: 256 bytes

Results

Inodes the filesystem will have: 30,517,578
Files expected at this average size: 7,629,394
Space consumed by the inode table: 7.28 GiB
Assessment: Sufficient inodes for the expected file count

Step by step

1Values used
2Inode budget
3Inodes the filesystem will have= 30,517,578
4Files expected at this average size= 7,629,394
5Space consumed by the inode table= 7,812,499,968
6Assessment= Sufficient inodes for the expected file count

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Can inodes be added later?

Not on ext4. You must back up, reformat with a lower bytes-per-inode value, and restore. Plan for the workload before formatting.

Which filesystem avoids this?

XFS and Btrfs allocate inodes dynamically, so they run out only when the disk is genuinely full. That is a strong argument for XFS on mail and cache servers.