Mount Point Capacity Calculator
Calculate available capacity across multiple mount points sharing an underlying volume.
About Mount Point Capacity Calculator
When a single disk is carved into separate mount points (either as distinct partitions or LVM logical volumes), each mount point's capacity is a fixed share of the underlying device — unlike directories on a shared filesystem, exceeding one mount point's allocation doesn't borrow from another. This calculator distributes total disk capacity across the standard Linux mount points (/boot, /, /home, /var, /tmp) by percentage share so you can plan partition sizes before running fdisk, parted or lvcreate.
Formula
Per-mount capacity
mount_capacity = total_capacity × allocation_percent
- T
- total disk capacity
- p_i
- allocation percentage for mount point i
Worked example
With the default values below, Mount Point Capacity Calculator returns Allocation Summary of 20 GB (4%) remains unallocated across mount points.. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Total Disk Capacity (GB)minimum 0
- 500
- /boot Allocation (%)accepts 0–100
- 1
- / (root) Allocation (%)accepts 0–100
- 20
- /home Allocation (%)accepts 0–100
- 40
- /var Allocation (%)accepts 0–100
- 30
- /tmp Allocation (%)accepts 0–100
- 5
Results
- Allocation Summary
- 20 GB (4%) remains unallocated across mount points.
- /boot
- 5.00 GB
- / (root)
- 100.00 GB
- /home
- 200.00 GB
- /var
- 150.00 GB
- /tmp
- 25.00 GB
- Unallocated
- 20.00 GB
Step by step
- 1Values used
- 2Per-mount capacity
- 3Allocation Summary= 20 GB (4%) remains unallocated across mount points.
- 4/boot= 5.00 GB
- 5/ (root)= 100.00 GB
- 6/home= 200.00 GB
- 7/var= 150.00 GB
- 8/tmp= 25.00 GB
Assumptions and limits
- The result is derived only from the 6 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 2 decimal places, 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
Why give /var its own partition?
/var holds logs, package caches and spool files that can grow unexpectedly (e.g. a runaway log). Isolating it on its own partition means a full /var can't consume all free space on / and crash the root filesystem or prevent login.
How big should /boot be?
/boot typically only needs 500MB-1GB even on modern systems, since it holds kernel images, initramfs and bootloader files. Percentage-based sizing works for planning, but /boot is usually better set to a fixed size regardless of total disk capacity.
Should swap be included as a mount point here?
No — swap space is a distinct partition type (or swap file) that isn't mounted into the directory tree, so it's sized separately. Use the Swap Size Calculator or Swap Partition Calculator for that allocation.