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Partition Size Plan Calculator

Work out partition size plan instantly with clear inputs, formula shown and shareable results.

About Partition Size Plan Calculator

Separating /var matters because logs and container images grow without bound and a full root filesystem prevents the system from functioning at all. Reserving about a gigabyte for the EFI system partition and /boot leaves room for several kernel versions. Using LVM for the rest means these boundaries can be adjusted later rather than being permanent.

Formula

Partition plan

usable = total - swap - boot reservation; root = usable x root share; /var = usable x var share; remainder to /home and data

Worked example

With the default values below, Partition Size Plan Calculator returns Root filesystem size of 98.2. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total disk sizeminimum 1 GB
500 GB
Root filesystem shareaccepts 1–100 %
20 %
/var shareaccepts 0–100 %
30 %
Swap sizeminimum 0 GB
8 GB

Results

Root filesystem size
98.2 GB
/var size
147.3 GB
Remaining for /home and data
245.5 GB
Reserved for EFI and /boot
1.0 GB

Step by step

  1. 1Values used
  2. 2Partition plan
  3. 3Root filesystem size= 98.2 GB
  4. 4/var size= 147.3 GB
  5. 5Remaining for /home and data= 245.5 GB
  6. 6Reserved for EFI and /boot= 1.0 GB

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 1 decimal place, 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 separate /var at all?

So runaway logs or container storage cannot fill the root filesystem. A full root breaks logging, package management and often SSH login.

Should I still use separate partitions with LVM?

LVM gives separate logical volumes that can be grown, which is the best of both worlds: isolation now and flexibility later.

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