Subnet Calculator
Calculate the network address, broadcast address, and usable host range from an IPv4 address and CIDR prefix.
Result
Enter an IP address and prefix
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How subnetting works
A CIDR prefix (like /24) defines how many bits of an IPv4 address are used for the network portion, leaving the rest for host addresses. This calculator applies the subnet mask to your IP address to find the network address, broadcast address, usable host range, and total number of usable hosts.
Common subnet sizes
| CIDR | Subnet mask | Usable hosts |
|---|---|---|
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
Frequently asked questions
- Why does /31 and /32 show 0 usable hosts?
- A /31 is used for point-to-point links (both addresses are usable per RFC 3021) and a /32 identifies a single host, so the usual network/broadcast math doesn't apply the same way.
- Does this support IPv6?
- Not currently — this calculator is built for IPv4 addresses and CIDR notation.