Subnet Calculator
Calculate IPv4 subnets: network address, broadcast address, subnet mask, usable hosts, and more.
IPv4 Subnet Calculator
Enter an IPv4 address and prefix (CIDR) to compute network details. You can use 192.168.1.10/24 or separate the IP and prefix.
If you typed /xx in the IP field, that will override this value.
What is a subnet?
A subnet is a logical subdivision of an IP network. It's defined by a network address and a subnet mask (or prefix length like /24).
CIDR notation (like 192.168.1.0/24) tells you:
- Network part – identifies the subnet.
- Host part – identifies devices within that subnet.
- Prefix length – how many bits belong to the network.
Common subnet sizes
| CIDR | Mask | Total | Usable* |
|---|---|---|---|
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /30 | 255.255.255.252 | 4 | 2 |
| /32 | 255.255.255.255 | 1 | 0 |
*Traditional IPv4 addressing reserves the network and broadcast addresses. Some point-to-point links use /31 subnets with two usable endpoints.