Subnet Calculator

Find the network, broadcast address, host range and netmask of any IPv4 or IPv6 subnet.

Runs in your browser. Nothing you enter is uploaded.

· Also reads masks like 10.0.0.5 255.255.0.0, and IPv6.

Enter an IP address to see its subnet

You get the network and broadcast address, the usable host range, the masks and the address type.

How to use Subnet Calculator

  1. Type an IP address with its prefix, like 192.168.1.10/24, or with a mask, like 10.0.0.5 255.255.0.0. IPv6 works too.
  2. Or type just the address and pick the subnet mask from the menu.
  3. Read the network address, broadcast address, usable host range, masks and address type.
  4. To plan a network, choose a size under Split into smaller subnets. To test an address, type it under Is an address in this subnet?
  5. Copy the results. The page address holds your subnet, so you can share the link.

How it works

An IP address has two parts: the network it belongs to and the device’s number in that network. The prefix (/24) or the subnet mask (255.255.255.0) says where the split is. From that, the calculator works out every address in the subnet. It all runs in your browser, so nothing you type is sent anywhere.

You can type the subnet in any common form:

  • CIDR: 192.168.1.10/24
  • Address and mask: 10.0.0.5 255.255.0.0, or 10.0.0.5/255.255.0.0
  • Wildcard mask: 10.1.2.3 0.0.0.255 is read as /24, with a note
  • IPv6: 2001:db8::1/64, with :: shortening and a zone index like %eth0

Reading the results

Result What it means
Network address The first address. It names the subnet and can’t be given to a device.
Broadcast address The last address. A message sent to it reaches every device in the subnet.
Usable host range The addresses you can give to computers, phones, printers and routers.
Wildcard mask The subnet mask flipped, as Cisco access lists and OSPF use it.
Address type Private, public, loopback, link-local and other special ranges.
Class The old A, B and C system. Networks have used prefixes (CIDR) instead since 1993, but the class still comes up in exams.

A /31 has no network or broadcast address, so both of its addresses are usable on a link between two routers. A /32 is a single address.

Splitting a network

Split into smaller subnets divides your subnet into equal parts. A /24 split into /26 gives 4 subnets of 64 addresses, each with 62 usable hosts. The list shows each subnet’s usable range and broadcast address, up to the first 256.

IPv4 prefix cheat sheet

Each prefix has twice as many addresses as the next one, and 2 fewer usable hosts than addresses (except /31 and /32).

Prefix Subnet mask Usable hosts
/8 255.0.0.0 16,777,214
/9 255.128.0.0 8,388,606
/10 255.192.0.0 4,194,302
/11 255.224.0.0 2,097,150
/12 255.240.0.0 1,048,574
/13 255.248.0.0 524,286
/14 255.252.0.0 262,142
/15 255.254.0.0 131,070
/16 255.255.0.0 65,534
/17 255.255.128.0 32,766
/18 255.255.192.0 16,382
/19 255.255.224.0 8,190
/20 255.255.240.0 4,094
/21 255.255.248.0 2,046
/22 255.255.252.0 1,022
/23 255.255.254.0 510
/24 255.255.255.0 254
/25 255.255.255.128 126
/26 255.255.255.192 62
/27 255.255.255.224 30
/28 255.255.255.240 14
/29 255.255.255.248 6
/30 255.255.255.252 2
/31 255.255.255.254 2
/32 255.255.255.255 1

IPv6

IPv6 has no broadcast address, so every address in a subnet is usable. Home and office networks almost always use a /64, which holds 18,446,744,073,709,551,616 addresses. Internet providers usually hand customers a /48 or a /56, which the calculator shows as a number of /64 networks. Addresses starting with fe80 are link-local and only work on the local network; addresses starting with fd are private, like 192.168 addresses in IPv4.

Questions

How do I calculate a subnet mask from a prefix?

The prefix is how many bits of the mask are 1. Each full group of 8 ones is 255, so /24 is 255.255.255.0 and /16 is 255.255.0.0. A partial group is 128, 192, 224, 240, 248, 252 or 254 for 1 to 7 ones: /26 is 255.255.255.192.

How many usable hosts are in a /24?

254. A /24 has 256 addresses, and two are reserved: the first is the network address and the last is the broadcast address. In general, a subnet has 2^(32 − prefix) addresses and 2 fewer usable hosts. A /31 is the exception, with 2 usable addresses, and a /32 is a single address.

What does /24 mean in an IP address?

It is CIDR notation: the first 24 bits of the address are the network part and the remaining 8 bits number the devices. So 192.168.1.10/24 is device 10 in the network 192.168.1.0, which has 256 addresses.

What is a wildcard mask?

The opposite of a subnet mask: every 1 becomes 0 and every 0 becomes 1, so 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use wildcard masks. Type one after an address and the calculator reads it.

What is a private IP address?

An address from the ranges 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. They work only inside a network, never on the internet, so every home router can use them. The router shares one public address among its devices (NAT).

Why does my computer have a 169.254 IP address?

It got no address from your router, so it gave itself a link-local one, which can’t reach the internet. Check the cable or Wi-Fi connection and restart the router. On Windows, ipconfig /release and then ipconfig /renew asks the router again.

Updated October 19, 2026 · Works in current Chrome, Edge, Firefox and Safari · Runs entirely in your browser