--- title: Chmod Calculator: Octal & Symbolic description: Free chmod calculator. Flip rwx checkboxes and get the octal number, symbolic notation and ready-to-run chmod command — or type 755 and see exactly what it grants. Covers setuid, setgid and the sticky bit. canonical: https://watchfor.io/chmod-calculator --- [Back to all free tools](/free-tools) # Chmod Calculator Unix file permissions without the head-scratching — flip the rwx checkboxes and get the octal number, symbolic notation and ready-to-run chmod command, or type 755 and see exactly what it grants. Covers setuid, setgid and the sticky bit, with presets for the permissions you actually use. Free, no signup. [How to use this tool](/blog/how-to-calculate-chmod-permissions) Permissions   Read ( 4 ) Write ( 2 ) Execute ( 1 ) Digit Owner 7 Group 5 Others 5 setuid setgid sticky Octal (type to set, e.g. 644 or 2775) Octal 755 Symbolic rwxr-xr-x chmod 755 filename Common permissions 755 · Scripts & directories 644 · Regular files 700 · Private directory 600 · Private file (keys) 750 · Group-shared directory 640 · Group-readable file 777 · Everyone everything ## Reading ls -l output -rwxr-xr-- breaks down as: file type ( - file, d directory, l symlink), then three triplets for owner ( rwx ), group ( r-x ) and others ( r-- ) — which is 754 in octal. An s in an execute position means setuid/setgid, a t in the last position is the sticky bit. Octal Symbolic Typical use 755 rwxr-xr-x Executables, web directories 644 rw-r--r-- Web files, configs readable by services 700 rwx------ Private directories (~/.ssh) 600 rw------- Private keys, credentials 750 rwxr-x--- Group-shared tools 1777 rwxrwxrwt /tmp — world-writable with sticky bit ## Frequently asked questions What does chmod 755 mean? 755 grants the owner read, write and execute (7 = 4+2+1), and everyone else read and execute (5 = 4+1). In symbolic form: rwxr-xr-x. It's the standard permission for executables and directories that others may enter but not modify — which is why web servers expect 755 on directories and 644 on files. How do the octal digits map to permissions? Each digit is a sum of read=4, write=2, execute=1, and the three digits apply to the file's owner, its group, and everyone else, in that order. So 640 = owner rw (4+2), group r (4), others nothing (0). Once you internalise 4-2-1, you can read any mode at a glance. Why is chmod 777 dangerous? 777 lets every user on the system modify and execute the file — any compromised process or account can replace your script with a malicious one, and web servers will happily run it. It's usually applied out of frustration when something "doesn't work"; the correct fix is almost always changing the owner (chown) or group instead of opening the file to the world. Practically no production scenario needs 777. What does execute mean on a directory? On directories the bits change meaning: read lists the filenames, execute lets you enter the directory and access files inside (traverse), and write lets you create, rename and delete entries. A directory with execute but not read acts as a pass-through: you can open files you know the names of, but can't list what's there. That's why directories usually need 755 rather than 644. What are setuid, setgid and the sticky bit? They're a fourth, leading octal digit (setuid=4, setgid=2, sticky=1). Setuid makes an executable run with the file owner's privileges (how passwd edits a root-owned file). Setgid on a directory makes new files inherit the directory's group — the standard trick for shared project folders. The sticky bit on a world-writable directory (like /tmp, mode 1777) means only a file's owner can delete it. What's the difference between numeric and symbolic chmod? Numeric mode (chmod 644 file) sets all bits at once. Symbolic mode (chmod u+x file, chmod go-w file) adjusts specific bits relative to what's already there: u/g/o/a selects owner/group/others/all, +/-/= adds, removes or sets exactly. Symbolic is safer for surgical changes (adding execute without touching anything else), numeric for asserting a known-good state. Is chmod -R 777 ever the right fix for a permission error? No — it trades one visible error for a silent security hole. Diagnose instead: ls -l shows who owns the file, id shows who you are; the usual fixes are chown -R to the service user, adding your user to the right group, or 755/644 with correct ownership. If a vendor's install guide says chmod 777, treat it as a red flag about the vendor. ## Permissions fixed — is the service actually up? Half of all "permission denied" incidents are found by users, not admins. WatchFor checks your sites, APIs and servers around the clock and alerts you the moment something stops working. [Start monitoring for free](/pricing) Free plan · 15 monitors · no credit card required --- Canonical page: https://watchfor.io/chmod-calculator · Site guide: https://watchfor.io/llms.txt