🌐 Subnet Calculator
Calculate the network, broadcast, host range, and mask for any IPv4 subnet.
What is a subnet calculator?
A subnet calculator takes an IPv4 address and a CIDR prefix (like /24) and works out everything that follows from it: the network address, the broadcast address, the range of usable host addresses, how many hosts the subnet can hold, and the subnet and wildcard masks. It saves you from doing binary math by hand every time you plan or troubleshoot a network.
How to use it
- Type an IPv4 address (for example
192.168.1.10). - Choose the CIDR prefix from
/0to/32. - Read off the network, broadcast, host range, and masks instantly — all calculated in your browser.
Quick reference
- Network address — the first address in the block; identifies the subnet itself.
- Broadcast address — the last address; used to reach every host in the subnet.
- Usable hosts — total addresses minus the network and broadcast (except
/31and/32, which are special cases). - Wildcard mask — the inverse of the subnet mask, used in tools like access control lists.
Want to go deeper? Read our guides on ports and protocols and how NAT works.
Frequently asked questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation writes an IP address followed by a slash and a number, like 192.168.1.0/24. That number is the prefix length — how many bits from the left are fixed as the network portion. A larger prefix (say /28) means a smaller network with fewer hosts; a smaller prefix (/16) means a much larger one.
How many hosts does a /24 have?
A /24 contains 256 total addresses but 254 usable hosts, because the first address is the network address and the last is the broadcast address. In general, usable hosts = 2(32 − prefix) − 2 for any prefix up to /30.
What's the difference between /30, /31 and /32?
A /30 gives 2 usable hosts and is common for point-to-point links. A /31(RFC 3021) is a special case with just 2 addresses and no separate network/broadcast, also used for point-to-point links. A /32 is a single host — one exact address.
Which address ranges are private?
Three IPv4 blocks are reserved for private networks: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Addresses in these ranges aren't routable on the public internet and are what your router hands out at home or in the office.