Subnet Calculator
Enter any IP address and CIDR prefix to see the network address, broadcast address, usable host range and subnet mask instantly. Works for IPv4 and IPv6, right in your browser. Nothing is sent to a server.
- Network address
- 216.73.217.0
- Broadcast address
- 216.73.217.255
- Usable range
- 216.73.217.1 - 216.73.217.254
- Subnet mask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Total addresses
- 256
- Usable hosts
- 254
- IP class
- C
- Address type
- Public
- IP in binary
- 11011000.01001001.11011001.01110000
- Mask in binary
- 11111111.11111111.11111111.00000000
Subnet cheat sheet
The CIDR prefixes you will actually meet, with their masks and usable host counts.
| CIDR | 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 |
| /12 | 255.240.0.0 | 1,048,574 |
| /16 | 255.255.0.0 | 65,534 |
| /20 | 255.255.240.0 | 4,094 |
| /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 |
What is VLSM?
VLSM (variable-length subnet masking) means using different prefix sizes inside one network, so each subnet gets only the addresses it needs. Example: split 192.168.1.0/24 into a /26 for 60 office PCs (62 usable hosts), a /28 for 14 printers (14 usable), and a /30 for a router-to-router link (2 usable). Without VLSM every subnet would waste addresses on a one-size-fits-all mask.
Subnetting basics
Every IPv4 address has a network part and a host part. The subnet mask (or the /number in CIDR notation) says where the split is. Devices on the same subnet talk directly; traffic to another subnet goes through a router. Your own public IP address sits inside your ISP's much larger subnets, which is how routing stays manageable across the whole internet.
Frequently asked questions
What is a subnet calculator?
A subnet calculator splits an IP address and CIDR prefix into its network parts: the network address, broadcast address, usable host range, subnet mask and how many hosts fit. Network admins use it to plan subnets without doing binary math by hand.
What does /24 mean in an IP address?
The /24 is CIDR notation: the first 24 bits are the network part and the last 8 bits are for hosts. A /24 gives 256 total addresses and 254 usable hosts, with mask 255.255.255.0.
How many hosts are in a /24 subnet?
254 usable hosts. A /24 has 256 total addresses, minus the network address and the broadcast address. See the cheat sheet above for other prefix sizes.
What is the difference between a subnet mask and a wildcard mask?
They are inverses. Where the subnet mask has 1s, the wildcard mask has 0s. A /24 mask of 255.255.255.0 pairs with wildcard 0.0.0.255. Wildcard masks show up in router access lists.
Do I need to subnet my home network?
No. Home routers hand out one /24 and that is plenty. Subnetting matters for offices, labs and certifications, where one network must be split into smaller pieces.