Docker Compose Generator
Build a docker-compose.yml with databases, caches and health checks.
Chmod Calculator
Convert file permissions between octal, symbolic and checkboxes.
Octal like 755 or 4755, or symbolic like rwxr-xr-x — either is accepted, and the boxes below follow.
| Who | Read 4 | Write 2 | Execute 1 | Digit |
|---|---|---|---|---|
| Owner | 7 | |||
| Group | 5 | |||
| Everyone else | 5 |
Quick Tool Overview
The Chmod Calculator converts between the three ways Unix permissions get written — 755, rwxr-xr-x and a grid of checkboxes — including the fourth digit that carries setuid, setgid and the sticky bit, and why an s sometimes appears where you expected an x.
- What it does
- Converts file permissions between every notation
- You give it
- An octal or symbolic mode, or ticked boxes
- You get back
- Every form, a breakdown and the chmod command
- Best for
- Fixing a permissions problem without reaching for 777
About the Chmod Calculator
Tick the boxes and get the octal; type the octal and see what it grants. This converts between the three ways Unix file permissions get written — 755, rwxr-xr-x and a grid of checkboxes — and explains what each one gives to whom.
Once you see it as bits, the octal stops needing to be memorised: read is 4, write is 2, execute is 1, and each digit is those added together for the owner, the group and everyone else. A fourth leading digit, when present, carries setuid, setgid and the sticky bit — which is why an `s` or a `t` sometimes appears where you expected an `x`, and why 4755 and 755 are very different things. The calculator flags the modes that are almost always a mistake, and gives the umask that would produce the mode you have chosen.
Key features of the Chmod Calculator
All three notations
Octal, symbolic and checkboxes, each updating the others, so the arithmetic behind 755 becomes visible rather than memorised.
The special bits
setuid, setgid and sticky, with the capital S and T that mean the bit is set without execute — the detail that makes 4644 confusing.
Warnings where they belong
World-writable files and setuid binaries are flagged, and 777 is called what it is: a symptom whose real cause is usually ownership.
The command, ready to run
Both the plain and the recursive form, so nobody has to remember which flag is which.
The matching umask
The umask value that would create files with the mode you have chosen, which is how you set it once instead of per file.
How to use the Chmod Calculator
-
1
Enter a mode
Octal like 755 or 4755, or symbolic like rwxr-xr-x — either is accepted.
-
2
Or tick the boxes
Read, write and execute for owner, group and other, plus the special bits.
-
3
Read the breakdown
What each class of user can do, and warnings for the modes that are usually wrong.
-
4
Copy the command
The chmod command is generated, with the recursive form alongside it.
Frequently asked questions
The owner can read, write and execute; the group and everyone else can read and execute but not write. It is the normal mode for a directory, a script or a program — read plus execute is what lets you enter a directory and list what is in it.
It lets any user on the machine modify the file, including replacing a script that something else runs. It is almost always applied to fix a permissions error whose real cause is ownership — chown is usually the correct answer.
setuid (4), setgid (2) and the sticky bit (1). setuid makes a program run as its owner rather than as whoever launched it. setgid makes new files in a directory inherit its group. The sticky bit — 1777 on /tmp — lets everyone write but only the owner delete.
Because on a directory, execute means "may enter", not "may run". Read without execute lets you list the names inside and nothing else; execute without read lets you open a file whose exact path you already know.
Reviews of the Chmod Calculator
What people who use the Chmod Calculator think of it. Reviews come from visitors and are posted as written.
No ratings yet
Yours would be the first.
- 5 0 reviews rated 5 stars
- 4 0 reviews rated 4 stars
- 3 0 reviews rated 3 stars
- 2 0 reviews rated 2 stars
- 1 0 reviews rated 1 star
0 reviews
Newest first
No reviews yet
Be the first to rate the Chmod Calculator. It takes half a minute and no account.
Write the first reviewMore developer tools
Punycode Converter
Convert internationalised domain names to punycode and back.
JWT Generator
Build and sign a JWT with HS256, HS384 or HS512 for testing.
Cubic Bezier Generator
Draw an easing curve and see it against the standard ones.
HTML Table Generator
Build an accessible HTML table from pasted data or by hand.
Browser Info Checker
Your browser, engine, platform, languages and what it supports.
Query String Builder
Build and edit URL query strings without breaking the encoding.
User Agent Parser
Break a user agent string into browser, engine, operating system and device.