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All calculatorsMethodology

Linux Chmod Calculator

Encode Unix owner, group and others permission checkboxes or decode three octal digits. Preserve leading zero groups and explain rwx meanings without changing files.

Interactive calculator · Method CHMOD-2.1 · Last reviewed: 2026-11-04

Estimate a technical storage or hardware value

This technical calculator uses visible units and deterministic formulas to estimate capacity, transfer time, latency, or hardware planning values.

Your inputs

Try an example

Three digits 0–7. This shows Unix owner, group and others bits; no command is executed.

Owner

Group

Public

Default worked example. Edit the inputs to calculate your scenario.

Default worked example

Numeric mode 755
Symbolic mode rwxr-xr-x
Illustrative command chmod 755 file
Owner rwx
Group r-x
Others r-x

Each permission digit adds read=4, write=2 and execute=1. Leading zero groups are preserved. The command is an illustration; no files are changed.

How to use the calculator

Encode requested permission triplets with checkboxes for owner, group and others, or decode exactly three octal digits from 0 to 7. The active entry mode determines the result; values in the inactive mode do not change it.

What the result means

The numeric and symbolic rows describe the requested permission triplet. The command is an illustration using the literal placeholder file; this page neither inspects nor changes files. For directories, execute/search permits traversal and read permits listing names.

Formula and units

Each triplet adds read = 4, write = 2 and execute/search = 1. The three octal digits encode owner, group and others in that order. Symbolic rwx groups use a dash for each unselected bit. Leading zero groups are retained, including mode 000.

Worked examples

Three octal permission digits: 755 three octal digits; ownerr: yes: Three octal permission digits: 755 three octal digits; ownerr: true; ownerw: true; ownerx: true; groupr: true; groupw: false; groupx: true; publicr: true; publicw: false; publicx: true; Permission entry mode: checkboxes.
Example result: Numeric mode: 755; Symbolic mode: rwxr-xr-x; Illustrative command: chmod 755 file; Owner: rwx; Group: r-x; Others: r-x.

Three octal permission digits: 755 three octal digits; ownerr: yes: Three octal permission digits: 755 three octal digits; ownerr: true; ownerw: true; ownerx: true; groupr: true; groupw: false; groupx: true; publicr: true; publicw: false; publicx: true; Permission entry mode: octal.
Example result: Numeric mode: 755; Symbolic mode: rwxr-xr-x; Illustrative command: chmod 755 file; Owner: rwx; Group: r-x; Others: r-x.

Limitations and common mistakes

ACLs, special mode bits, ownership and parent directory permissions can affect actual access. Directory entry changes require the relevant directory permissions and other filesystem rules. Three-digit encoding does not inspect or model those conditions.

Octal digits range from 0 to 7. Do not enter decimal permission sums, four-digit special-bit modes or symbolic chmod expressions here, or treat a displayed triplet as a universal access-policy recommendation.

Sources and assumptions

The mapping is a Unix permission identity; it does not inspect the target file or recommend access policy.

Method CHMOD-2.1; last formula review 2026-11-04. Sources and their supported claims. Calculation methodology.

GNU Coreutils: numeric permission modes. Owner, group and others each use read/write/execute bits. The installed GNU manual version 9.7 was inspected; special mode bits and actual access policy are outside this tool.