Calculators
Subnet, chmod, umask, energy, semver and permission calculators that show their working.
The calculators here all share one rule: show the working, not just the answer. A subnet calculator that prints a CIDR and nothing else is only useful if you already know the answer, so this one shows the binary, the range, the usable host count and why the broadcast address is excluded. A chmod calculator shows the octal and the symbolic form at once, plus what each triple means for the owner, the group and everyone else.
Use the subnet calculator when you are planning a network rather than looking up an existing one, the chmod and umask tools when permissions are wrong and you need the exact octal, and the energy/solar calculator when you are sizing a system rather than reading a spec sheet. The IPv6 tool exists because compressed and expanded forms of the same address look nothing alike, which makes diffing two configs by eye unreliable.
Where a calculation depends on an assumption - usable hosts, power draw, panel efficiency - the assumption is stated next to the number. If a result looks surprising, it is usually the input unit rather than the maths: hours versus minutes, bits versus bytes, and decimal versus binary prefixes are the three that catch people.
6 tools in this category
- Energy Calculator — Calculate energy usage and solar savings.
- IP Address & Subnet Calculator — CIDR, subnet mask, ranges & binary for IPv4/IPv6.
- IPv6 Compression & Expansion Tool — Convert IPv6 between expanded & RFC 5952 compressed, with validation & component
- Chmod Permission Calculator — Convert file permissions between octal, symbolic & plain-English, with ls -l preview &
- Linux Umask Calculator — Convert a umask into the file and directory permissions it produces: octal or symbolic
- Linux Permission Visualiser — See what read, write and execute mean for owners, groups and others: paste an ls -l
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