Subnet Calculator
Calculate network, broadcast, usable range, mask and host count for any IPv4 CIDR — and network range for IPv6 — entirely in your browser.
Split a /24 into smaller subnets
Load 192.168.1.0/24 with a target of 25 hosts per subnet and see the network mask, usable range, and how it splits.
FAQ
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) writes an IP plus a slash and the number of network bits, e.g. 192.168.1.0/24. The /24 means the first 24 bits are the network part; the rest identify hosts.
How many hosts fit in a /24?
A /24 has 256 addresses, but the first (network) and last (broadcast) are reserved, leaving 254 usable host addresses.
What is the difference between total and usable hosts?
Total is every address in the block. Usable subtracts the network and broadcast addresses (and on small blocks, any extra reserved ones), giving the number you can actually assign to devices.
What about IPv6?
IPv6 uses the same CIDR idea but with 128-bit addresses and enormous pools, so the calculator reports network ranges rather than worrying about usable-host counts.