Calculate an IPv4 Subnet
Enter an IPv4 address with a CIDR suffix, such as 192.168.1.10/24, or enter the address and prefix separately. Choose Calculate subnet to see the network address, broadcast address, subnet mask, wildcard mask, first and last usable hosts, address counts and binary mask. Each octet must be a decimal integer from 0 through 255 and the prefix must be from 0 through 32.
Network Masks and Address Counts
The prefix selects the network bits. The remaining bits determine the block size, which is 2 raised to 32 minus the prefix. For ordinary multi-access subnet arithmetic, the lowest address is the network and the highest is the broadcast, leaving two fewer usable addresses. Calculations use exact integer arithmetic and do not perform DNS resolution, geolocation, connectivity tests or any remote IP lookup.
Special /31 and /32 Prefixes
For /31, both addresses are shown as usable endpoints under the point-to-point convention in RFC 3021; there is no directed broadcast. A /32 represents one address, so its first and last host are identical and its usable count is one. A /0 covers the complete IPv4 address space. Counts describe mathematical ranges, not a promise that reserved or special-purpose addresses can be assigned on a real network.
Standards and references
Frequently asked questions
Does this calculator support IPv6?
No. This version accepts dotted-decimal IPv4 addresses only.
How does it handle a /31?
It treats both addresses as usable point-to-point endpoints and reports no directed broadcast, following RFC 3021.
What does a /32 mean?
A /32 is a single address. The network, first host and last host are the same, with one usable address.
Does it look up the IP owner or location?
No. All results are mathematical calculations performed locally in your browser.