Subnet calculator
Enter an IPv4 address and a prefix, and get the whole subnet worked out instantly — network and broadcast addresses, the usable host range, subnet and wildcard masks, host counts, and the binary breakdown. No account, nothing to install.
| Network address | 192.168.1.0 |
|---|---|
| Usable host range | 192.168.1.1 – 192.168.1.254 |
| Broadcast address | 192.168.1.255 |
| Subnet mask | 255.255.255.0 |
| Wildcard mask | 0.0.0.255 |
| Usable hosts | 254 |
| Total addresses | 256 |
| CIDR notation | 192.168.1.0/24 |
| IP class | C |
| Address type | Private (RFC 1918) |
11000000.10101000.00000001.0000101011111111.11111111.11111111.00000000The mask’s 1 bits are the network; the 0 bits are the host.
What the results mean
- Network & broadcast — the first and last address in the block. Neither is assignable to a host; the network names the subnet and the broadcast reaches every host on it.
- Usable host range — the addresses you can actually assign, from network + 1 to broadcast − 1 (a /31 and /32 are the special cases).
- Subnet mask & wildcard mask — the mask splits network from host; the wildcard (its inverse) is what OSPF and ACLs match on.
- Binary — line the address up under the mask: where the mask shows
1s is the network, where it shows0s is the host. That boundary is the whole game.
Subnet calculator FAQ
What does this subnet calculator work out?
Enter any IPv4 address and a prefix length (or subnet mask) and it instantly returns the network (subnet) address, the broadcast address, the first and last usable host, the subnet and wildcard masks, the number of usable hosts and total addresses, the IP class, and whether the address is public or private — plus the address and mask in binary so you can see the network/host boundary.
What is the difference between a subnet mask and a wildcard mask?
A subnet mask marks the network bits with 1s and host bits with 0s (for example 255.255.255.0 for a /24). A wildcard mask is its exact inverse — 255.255.255.255 minus the subnet mask — so a /24 becomes 0.0.0.255. Cisco uses wildcard masks in OSPF network statements and in ACLs, and mixing the two up is a very common cause of a rule matching the wrong traffic.
How many usable hosts are in a subnet?
For a normal subnet, usable hosts = 2^(host bits) − 2, because you subtract the network address and the broadcast address. So a /24 has 254, a /26 has 62, and a /30 has 2. The exceptions are a /31, which carries 2 usable addresses for point-to-point links (RFC 3021), and a /32, a single-host route.
Should I still learn to subnet by hand?
Yes. A calculator is perfect for checking your work and planning quickly, but the CCNA exam is timed and gives you none — and neither does a live console. Use this to verify, then drill the arithmetic on the free subnetting practice tool until the block-size method is second nature.
More free tools
VLSM Calculator →
Allocate variable-length subnets from a base network by per-subnet host requirement, largest-first.
Subnetting Practice →
Random CCNA-style subnetting questions, graded the instant you answer, with a streak counter.
Well-Known Ports →
A searchable TCP/UDP port reference — SSH 22, DNS 53, HTTPS 443 — plus a quiz to drill them.
OSI Model Quiz →
A protocol or device appears; you pick the right OSI layer. Instant feedback and a streak.
Try the Grader →
Edit a real Cisco IOS config in your browser and get instant per-requirement pass/fail.
Don’t just calculate it — be able to do it
Checking your work here is smart; being able to subnet without a calculator is what passes the CCNA.