Subnet Calculator

Enter an IPv4 address with a CIDR prefix or a subnet mask to see the network address, broadcast address, usable host range, wildcard mask, IP class and binary form — all calculated instantly in your browser.

How to use

1. Type an IPv4 address, for example 192.168.1.10.
2. Pick a CIDR prefix (for example /24) or type a subnet mask — the two stay in sync.
3. Press Calculate or just type; the results table updates instantly.
4. Use Copy results to get a plain-text summary for your notes.

What CIDR notation means

An IPv4 address has 32 bits. CIDR notation adds a slash and a number after the address, such as 192.168.1.0/24. The number — the prefix length — says how many of the 32 bits are the network portion. The remaining bits are the host portion. A /24 leaves 8 host bits, giving 256 total addresses; a /16 leaves 16 host bits, giving 65,536 addresses; a /30 leaves 2 host bits, giving 4 addresses, commonly used for point-to-point links.

Why subnetting matters

Subnetting splits a large network into smaller, separate groups. This limits broadcast traffic to each segment, improves security by isolating groups of devices, and lets routers handle smaller routing tables. It also prevents address waste: instead of giving a small office a full /24 (256 addresses), you can assign a /28 (16 addresses) and use the rest elsewhere.