Subnet Calculator

A subnet calculator is an essential tool for network engineers and sysadmins working with IPv4 addressing. Enter an IP address and a CIDR prefix length (e.g. /24) to instantly compute the network address, broadcast address, first and last usable host IPs, subnet mask, and the total number of hosts in that subnet. No installation needed — everything runs in your browser.

IP Address

CIDR Prefix

Common Subnet Masks Reference

/8 = 255.0.0.0 — 16,777,214 hosts (Class A) /16 = 255.255.0.0 — 65,534 hosts (Class B) /24 = 255.255.255.0 — 254 hosts (Class C) /25 = 255.255.255.128 — 126 hosts /26 = 255.255.255.192 — 62 hosts /27 = 255.255.255.224 — 30 hosts /28 = 255.255.255.240 — 14 hosts /29 = 255.255.255.248 — 6 hosts /30 = 255.255.255.252 — 2 hosts /31 = 255.255.255.254 — 2 hosts (P2P, RFC 3021) /32 = 255.255.255.255 — 1 host (single host)