IP Subnet / CIDR Calculator
Enter an IPv4 address with a CIDR prefix (like 192.168.1.0/24) — or an address and subnet mask, like 192.168.1.10 255.255.255.0 — to get the network address, broadcast address, usable host range, and host count.
Last updated
How to calculate a subnet
- Type an IPv4 address with a CIDR prefix, such as
192.168.1.0/24, or an address and subnet mask. - Read the network and broadcast addresses, the usable host range and the number of hosts.
How it's calculated
The CIDR prefix (/n) sets how many leading bits of the 32-bit address are the network portion; the rest are host bits. The network address zeroes out the host bits, the broadcast address sets them all to 1, and everything in between (minus those two, for prefixes shorter than /31) is a usable host address. Runs entirely in your browser — no address is looked up or sent anywhere.
Questions about subnets
How many hosts are in a /24?
256 addresses, of which 254 are usable: the first is the network address and the last is the broadcast address.
What is the subnet mask for /24?
255.255.255.0. A /16 is 255.255.0.0, and a /28 is 255.255.255.240 (16 addresses, 14 usable).
What does CIDR notation mean?
The number after the slash is how many bits of the 32-bit address identify the network; the rest identify hosts.
What are private IP ranges?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16, used inside home and office networks and not routed on the internet.