Network
Subnet Calculator
Work out the network address, broadcast address, and usable host range for any IPv4 CIDR block.
Related: look up where a specific address in that range is located.
Runs entirely in your browser. Nothing you enter is sent anywhere.
Learn about IPv4 subnetting
What the prefix actually controls
A CIDR block like 192.168.1.0/24 splits a 32-bit IPv4 address into a fixed network portion and a variable host portion. The /24 means the first 24 bits are fixed for the network, leaving 8 bits free for host addresses. The network address is that block with every host bit set to 0. The broadcast address is the same block with every host bit set to 1. Everything in between is a usable host address.
Quick reference
| Prefix | Total addresses | Usable hosts |
|---|---|---|
| /24 | 256 | 254 |
| /25 | 128 | 126 |
| /26 | 64 | 62 |
| /27 | 32 | 30 |
| /28 | 16 | 14 |
| /29 | 8 | 6 |
| /30 | 4 | 2 |
| /31 | 2 | 2 (point-to-point) |
| /32 | 1 | 1 (single host) |
Common questions
Why is the usable host count 2 less than the block size? The first address in the block is reserved as the network address and the last as the broadcast address, so neither can be assigned to a device. Every other prefix follows this rule.
What's special about /31 and /32? RFC 3021 carved out an exception for /31. Since a point-to-point link (like a router-to-router connection) only ever has two devices and no broadcast, both addresses are usable instead of reserving one. A /32 identifies a single specific host, commonly used for loopback interfaces or individual host routes.
How is this different from the CIDR / Mask Converter? That tool just converts between CIDR notation and a dotted-decimal mask, the same information written two ways. This one goes further and computes the actual network, broadcast, and usable-range addresses for a specific block.