/24 · 255.255.255.0
Open in the calculator
The most familiar size: 256 addresses, 254 usable, mask 255.255.255.0 (the old "class C"). 192.168.1.0/24 is the default on most home routers. In a /24 the network address ends in .0 and the broadcast in .255; the usable hosts are .1 to .254.
Key numbers
| Prefix length | /24 (24 network bits, 8 host bits) |
| Subnet mask | 255.255.255.0 |
| Mask in binary | 11111111.11111111.11111111.00000000 |
| Wildcard mask | 0.0.0.255 |
| Total addresses | 256 |
| Usable hosts | 254 (total minus network and broadcast) |
| Block size | Increments of 1 in octet 3 |
Example ranges
Private (RFC 1918) blocks of this size. Click one to open it in the calculator.
| Block | First address | Last address | Usable hosts |
|---|---|---|---|
| 10.0.0.0/24 | 10.0.0.0 | 10.0.0.255 | 10.0.0.1 – 10.0.0.254 |
| 172.16.0.0/24 | 172.16.0.0 | 172.16.0.255 | 172.16.0.1 – 172.16.0.254 |
| 192.168.0.0/24 | 192.168.0.0 | 192.168.0.255 | 192.168.0.1 – 192.168.0.254 |
Usable addresses in the cloud
Cloud providers reserve a few addresses in every subnet for the router, DNS and future use, so the usable count is lower than the formula gives.
| Provider | Usable in a /24 | Notes |
|---|---|---|
| AWS VPC subnet | 251 | Allowed (/16 to /28). AWS reserves the first four addresses and the last one. |
| Azure virtual network subnet | 251 | Allowed. Azure reserves the first four addresses and the last one. |
| Google Cloud subnet | 252 | Allowed. Google Cloud reserves the first two and the last two addresses. |
How the numbers are derived
An IPv4 address has 32 bits. A /24 uses 24 of them for the network, leaving 8 host bits, so the block has 28 = 256 addresses. The first address (all host bits 0) is the network address and the last (all host bits 1) is the broadcast address, which leaves 254 for hosts. The subnet mask is 24 ones followed by 8 zeros, written in dotted decimal as 255.255.255.0; the wildcard mask 0.0.0.255 is its inverse, used in Cisco ACLs and OSPF configuration.
FAQ
How many hosts can a /24 have?
256 addresses in total, of which 254 are usable after removing the network and broadcast addresses. Cloud providers reserve a few more: 251 usable in AWS and Azure, 252 in Google Cloud.
What is the difference between /24 and 255.255.255.0?
None: they are two notations for the same mask. /24 counts the network bits; 255.255.255.0 shows them as a dotted mask.