IP and Subnet Calculator
Enter an IP address and a mask to get the network and broadcast addresses, the usable range and the number of devices, check whether two addresses can talk directly, and split a network into smaller subnets.
Binary view
Subnets
| Subnet | Usable range | Broadcast |
|---|
How it works
The mask splits the 32-bit address into a network part and a device part. The network address is the address with every device bit set to 0, the broadcast address has every device bit set to 1, and the usable addresses are everything between them: 2(32 − prefix) − 2 of them (a /31 gives two, for point-to-point links, and a /32 is one host). Two addresses are on the same subnet when they have the same network address; if not, they need a router. The wildcard is the mask turned inside out. The ideas are explained on IP Addressing, Subnets and VLANs.
Worked example
A machine network is 192.168.10.0 with mask 255.255.255.192 (/26). For the address 192.168.10.70 the calculator gives network 192.168.10.64, broadcast 192.168.10.127 and 62 usable addresses (192.168.10.65 to .126). Checking it against 192.168.10.10 shows No: 192.168.10.10 is in the block 192.168.10.0 to .63, so the two need a router. Choosing a /26 split of 192.168.10.0/24 lists the four subnets .0, .64, .128 and .192, each with 62 usable addresses.
Things to know
Only IPv4 is covered, which is what almost every control device uses. The calculator does not know your network: it never contacts any device.
The mask must be a run of 1 bits followed by 0 bits (a “contiguous” mask), written as /8 to /32. Other masks are not valid in modern networks.
The first and last addresses of a subnet are the network and broadcast addresses and cannot be given to a device (except in /31 and /32 networks).
Private ranges (10.x.x.x, 172.16 to 172.31, 192.168.x.x) are meant for use inside a plant and are not routed on the internet.
Common questions
How many devices fit in a /24?
A /24 has 256 addresses, of which 254 are usable. Use /25 for 126, /26 for 62, /27 for 30 and /28 for 14 usable addresses.
Why is my usable count two less than the total?
The first address names the network and the last is the broadcast address; neither can be given to a device.
What is a wildcard mask?
The inverse of the subnet mask (255.255.255.192 becomes 0.0.0.63). Some routers and firewalls use it to write access rules.
What does /26 mean?
The first 26 bits of the address are the network. It is the same as the mask 255.255.255.192.
Sources
- RFC 4632, Classless Inter-domain Routing (CIDR); RFC 950, Internet Standard Subnetting Procedure.
- RFC 1918, Address Allocation for Private Internets.
Last reviewed: October 22, 2026