IP Subnet Calculator
Work out network, broadcast, mask and usable host range for any IPv4 prefix.
A smaller number covers more addresses. /24 is the usual size for a home or office network.
Runs entirely in your browser — nothing is uploaded.
254 usable addresses in this range
About the IP Subnet Calculator
The Freemium.Tools IP subnet calculator turns an IPv4 address and CIDR prefix into the network address, subnet mask, broadcast address, usable host range and host count.
Planning a network means knowing exactly which addresses a prefix covers. Entering an address and moving the prefix slider shows the range instantly, so you can size a subnet before assigning anything.
The result also flags whether the address is private or publicly routable, and shows the binary form, which helps when you are learning how masks work.
How to use it
- 1Enter an IPv4 address. For example 192.168.1.10 or 10.0.4.25.
- 2Choose the prefix. Slide from /0 to /32; /24 is the usual size for a home or office network.
- 3Read the range. Network, mask, broadcast, first and last usable host, and the total count.
Frequently asked questions
Why are two addresses unusable?
In a normal subnet the first address identifies the network itself and the last is the broadcast address, so neither can be assigned to a device.
What does /24 mean?
The first 24 bits are the network portion, leaving 8 bits for hosts — 256 addresses, 254 of them usable.
Does it handle /31 and /32?
Yes. A /32 is a single host route and a /31 is a two-address point-to-point link, both treated as fully usable.
Which ranges count as private?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are private, plus 127.0.0.0/8 for loopback. Everything else is publicly routable.
Does it support IPv6?
Not yet — this calculator covers IPv4 addressing, which is where most subnetting questions arise.