SubnetCalc
Calculate subnet

IPv4 network arithmetic

IPv4 subnet calculator

Enter an IPv4 address with a CIDR prefix or contiguous subnet mask to see the exact network range, usable hosts, and binary boundary.

Private browser calculation

Address, prefix, and host sizing

Stays on this page

Calculation mode

IPv4 address and prefix

Use a separate prefix or mask, or enter address/prefix and leave the second field empty.

A /31 result is blocked until you explicitly confirm its two endpoint semantics. Other prefixes ignore this choice.

Exact unsigned 32-bit arithmetic runs locally. This tool does not query, scan, locate, or test any address, and it does not configure a device.