IP Subnet Calculator (IPv4 / CIDR)
Free IPv4 subnet calculator: enter an IP and CIDR prefix to get network address, broadcast, usable host range, subnet mask, wildcard mask and host count.
How this subnet calculator works
Enter any IPv4 address and choose a CIDR prefix (like /24). The calculator applies the subnet mask to find the network address (the first address of the block), the broadcast address (the last), and the usable host range between them. It also shows the dotted subnet mask, the wildcard mask used in ACLs, and whether the address is public, private (RFC 1918), CGNAT or loopback space.
Common home networks are /24 (254 hosts). Point-to-point links use /30 or /31. If subnetting is new to you, our guide to subnet masks explains what the numbers mean, and public vs private IPs covers the reserved ranges.
Frequently asked questions
What does /24 mean?
It's CIDR notation: the first 24 bits of the address identify the network, leaving 8 bits for hosts — 256 addresses, 254 of them usable (network and broadcast addresses are reserved).
Why are two addresses unusable in each subnet?
The all-zeros host address names the network itself and the all-ones address is the broadcast. The exceptions are /31 (both addresses usable on point-to-point links) and /32 (a single host).