Calculate Unix/Linux file permissions visually. Convert between numeric and symbolic notation.
Every file and directory in Unix/Linux has three permission groups: Owner (u), Group (g), and Others (o). Each group has three permissions: Read (r=4), Write (w=2), and Execute (x=1). The numeric value is the sum of enabled permissions for each group. For example, 7 = 4+2+1 = rwx (read + write + execute).
755 — standard for directories and executables (owner: full, others: read+execute). 644 — standard for files (owner: read+write, others: read-only). 600 — private files (owner only). 700 — private directories. 777 — full access for everyone (generally unsafe).
Directories require execute permission to be traversed. Without it, you can't list contents or cd into the directory. That's why directories typically use 755 (rwxr-xr-x) while regular files use 644 (rw-r--r--).