Subnet Calculator
Calculate IPv4 subnets from CIDR notation.
About Subnet Calculator
Calculate subnet details from an IP address and CIDR or netmask. Networking requires knowing a subnet's network address, broadcast address, usable host range, and total host count, and working those out from a mask by hand is slow and error-prone. Enter an IP with its CIDR prefix and this calculator instantly returns the full breakdown so you can plan address space, configure routers, or study for a certification with confidence. It is an everyday reference for network administrators and students alike. The calculation runs entirely in your browser, so nothing you enter is uploaded or stored, and the tool is completely free to use with no signup.
How to use this tool
- 1Enter an IPv4 address and CIDR prefix (e.g. 192.168.1.0/24).
- 2See the network details instantly.
CIDR prefix reference
CIDR notation (like /24) says how many bits of an IP address identify the network. The remaining bits identify hosts. Fewer prefix bits = bigger network.
| CIDR | Subnet mask | Usable hosts | Typical use |
|---|---|---|---|
| /30 | 255.255.255.252 | 2 | Point-to-point links |
| /29 | 255.255.255.248 | 6 | Tiny office blocks |
| /27 | 255.255.255.224 | 30 | Small subnets |
| /24 | 255.255.255.0 | 254 | Standard LAN / home network |
| /22 | 255.255.252.0 | 1,022 | Larger office networks |
| /16 | 255.255.0.0 | 65,534 | Campus / large private ranges |
Usable hosts = 2^(host bits) − 2, because the all-zeros address names the network and the all-ones address is broadcast. The private ranges reserved for internal use are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.
Frequently asked questions
What does the calculator show?
Network address, broadcast address, subnet mask, wildcard mask, usable host range, and total usable hosts.
Does it support IPv6?
This tool focuses on IPv4 subnetting. IPv6 support may be added later.