IPv4 Subnet Calculator Online — Free & Private

A free edge API by formatho.com, privacy-first developer tools.

Open the full browser tool →

Free, no signup, runs entirely in your browser — your data never leaves your device.

🔓 Free🔒 Zero tracking🚫 No data collection⚡ Edge-fast

Usage

curl "https://subnet-calculator-formatho.filesformatho.workers.dev/api?cidr=192.168.1.10/24"
# dotted mask also works
curl "https://subnet-calculator-formatho.filesformatho.workers.dev/api?ip=10.0.5.7&mask=255.255.255.0"

Returns network, broadcast, netmask, wildcard, first/last usable host, usable & total host counts, host bits, address class and private/reserved-range flags.

Full parameter reference: /api endpoint.

Privacy-first: addresses are computed in-memory at the edge and never logged or stored.

Full browser tool

Calculate subnets entirely client-side: IPv4 Subnet Calculator on formatho.com.

All Formatho edge APIs

Browse every free Formatho Worker tool on the Formatho Tools index.