What does chmod 755 actually mean?

755 grants the owner read, write and execute (7), while group and other each get read and execute but not write (5), which is the common permission set for an executable script or directory others should be able to enter.

How do the numbers 4, 2 and 1 turn into an octal digit?

Each permission has a fixed weight, read is 4, write is 2, execute is 1, and you add the weights of the bits that are on; owner rwx is 4+2+1=7, while read-execute only is 4+1=5.

What is the difference between the octal and symbolic forms?

Octal like 644 is three digits, one per scope, while symbolic like rw-r--r-- spells out each of the nine bits as r, w, x or a dash; both describe the exact same permission set, just in different notations.

Does this calculator handle setuid, setgid or the sticky bit?

No, it only computes the standard three-digit permission set for owner, group and other; special-permission bits that add a fourth leading digit, like 4755 for setuid, are outside what this tool tracks.

Chmod Calculator

Toggle Unix read/write/execute bits and get the octal and symbolic chmod, locally.

Local, Runs entirely in your browser, your data never leaves your device.

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Turn read, write and execute checkboxes into an octal chmod

Unix file permissions are three groups, owner, group and other, each with read, write and execute bits worth 4, 2 and 1. This calculator gives each group its own row of checkboxes and keeps the octal digits, the rwxr-xr-x symbolic string and the full chmod command in sync as you click, or lets you type an octal number and see the checkboxes update instead. The math is a handful of bitwise operations, so nothing about your file or path needs to leave the page.

How to use the Chmod Calculator

Tick read, write and execute for the owner, group and other rows as needed.
Watch the octal field, such as 755, update to match your selections automatically.
Or type a three-digit octal number directly and let the checkboxes reflect it.
Read the symbolic notation, like rwxr-xr-x, next to the octal value.
Copy the ready-made chmod command, or just the octal or symbolic value, with one click.

Only the standard three-digit octal form (0-7 per digit) is supported, so setuid, setgid and sticky-bit digits are not part of this calculator; a four-digit chmod like 4755 would need to be entered as three digits plus that leading digit handled separately.

The symbolic string always has 9 characters, three per scope in read/write/execute order, with a dash standing in for any bit that is off, matching the format ls -l prints in the permissions column.

Frequently asked questions

What does chmod 755 actually mean?: 755 grants the owner read, write and execute (7), while group and other each get read and execute but not write (5), which is the common permission set for an executable script or directory others should be able to enter.
How do the numbers 4, 2 and 1 turn into an octal digit?: Each permission has a fixed weight, read is 4, write is 2, execute is 1, and you add the weights of the bits that are on; owner rwx is 4+2+1=7, while read-execute only is 4+1=5.
What is the difference between the octal and symbolic forms?: Octal like 644 is three digits, one per scope, while symbolic like rw-r--r-- spells out each of the nine bits as r, w, x or a dash; both describe the exact same permission set, just in different notations.
Does this calculator handle setuid, setgid or the sticky bit?: No, it only computes the standard three-digit permission set for owner, group and other; special-permission bits that add a fourth leading digit, like 4755 for setuid, are outside what this tool tracks.