SubnetKit › /24 Subnet Calculator
/24 Subnet Calculator: how it works
A /24 is the subnet almost everyone meets first: 256 addresses, 254 of them usable for hosts, with the familiar mask 255.255.255.0. It maps neatly onto the last octet, which is why home routers, small offices and most lab topologies use it.
SubnetKit calculates all of it in the browser for free. The calculator above is already loaded with 192.168.1.0/24; change the address or prefix and every field updates as you type, with nothing sent to a server.
Worked example: 192.168.1.0/24
- Network address: 192.168.1.0
- First usable host: 192.168.1.1
- Last usable host: 192.168.1.254
- Broadcast: 192.168.1.255
- Subnet mask: 255.255.255.0 (binary: 24 ones followed by 8 zeros)
- Wildcard mask: 0.0.0.255
- Total addresses: 256 (2^8)
- Usable hosts: 254 (256 minus network and broadcast)
Any address in the range belongs to the same subnet; for instance 192.168.1.37/24 and 192.168.1.200/24 are on-link with each other and share the gateway, which is conventionally .1 or .254.
Splitting a /24 into smaller subnets
Borrowing host bits turns one /24 into several equal blocks. Each borrowed bit doubles the subnet count and halves the hosts:
- /25: 2 subnets × 126 hosts (192.168.1.0/25 and 192.168.1.128/25), mask 255.255.255.128
- /26: 4 subnets × 62 hosts (.0, .64, .128, .192), mask 255.255.255.192
- /27: 8 subnets × 30 hosts (.0, .32, .64 … .224), mask 255.255.255.224
- /28: 16 subnets × 14 hosts, mask 255.255.255.240
The split table in SubnetKit lists each block's network, first and last host and broadcast, and you can switch between "split by prefix" and "split by number of subnets" depending on how the question is phrased.
Frequently asked questions
How many hosts are in a /24?
254 usable hosts. The block has 256 addresses, but the first is the network address and the last is the broadcast address.
What is the subnet mask for /24?
255.255.255.0. The wildcard mask, used in Cisco ACLs and OSPF statements, is 0.0.0.255.
How many /24 subnets fit in a /16?
256. A /16 such as 10.5.0.0/16 contains 10.5.0.0/24 through 10.5.255.0/24.
Is a /24 the same as a Class C network?
In size, yes: a classful Class C network was 256 addresses. Since CIDR, /24 is just a prefix length and can be used in any address range, including former Class A or B space.
Looking for the full guide, tips and the complete FAQ? Read the main SubnetKit page.