Category: Developer tools
Subnet Calculator
Turn an IPv4 CIDR block into its network, mask and host range
Enter an address such as 192.168.1.10/24 to see the network and broadcast addresses, the subnet and wildcard masks, the host range and the address count. Calculated locally.
Everything on this page is processed in your browser. Nothing is uploaded.
What this tool does
A CIDR prefix says how many leading bits identify the network, and everything else follows from arithmetic on the 32-bit address. This tool applies that arithmetic and lays the result out: the network and broadcast addresses that bound the block, the subnet mask and its wildcard complement for ACLs, the first and last usable host, and how many addresses the block holds.
How to use it
- Type an IPv4 address with its prefix, for example 10.0.0.0/16.
- Read the network, broadcast, mask and wildcard values.
- Use the host range and address count to plan the allocation.
Privacy
This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.
Frequently asked questions
- Does this look my address up anywhere?
- No. Every value is computed from the digits you typed, in your browser. There is no WHOIS, DNS or geolocation lookup, and nothing is sent to a server.
- Why are two addresses missing from the usable host count?
- In a normal subnet the first address identifies the network and the last is the broadcast address, so neither can be assigned to a host. /31 and /32 blocks are the documented exceptions and are counted differently.
- What is a wildcard mask for?
- It is the bitwise inverse of the subnet mask, and it is the form that Cisco-style access lists and some routing protocols expect.