Subnets · free
CIDR calculator
Everything about an IPv4 block in CIDR notation.
- Network
- 192.168.1.0/24
- Address range
- 192.168.1.0 – 192.168.1.255
- Subnet mask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Broadcast
- 192.168.1.255
- First – last host
- 192.168.1.1 – 192.168.1.254
- Addresses
- 256
- Usable hosts
- 254
- Type
- Private (RFC 1918)
CIDR notation writes a block of addresses as its first address and the number of fixed leading bits: 192.168.1.0/24 fixes the first 24 bits, leaving 8 bits, or 256 addresses. Each step down in prefix length doubles the block.
In a normal subnet the first address is the network address and the last the broadcast address, so a /24 has 254 usable hosts. A /31 is used for point-to-point links with both addresses usable (RFC 3021), and a /32 is a single host.
| Prefix | Mask | Addresses |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 |
| /16 | 255.255.0.0 | 65,536 |
| /20 | 255.255.240.0 | 4,096 |
| /22 | 255.255.252.0 | 1,024 |
| /24 | 255.255.255.0 | 256 |
| /26 | 255.255.255.192 | 64 |
| /28 | 255.255.255.240 | 16 |
| /30 | 255.255.255.252 | 4 |
| /32 | 255.255.255.255 | 1 |
What is the difference between a subnet mask and a wildcard mask?
They are bitwise opposites. The subnet mask marks the fixed network bits with ones (255.255.255.0 for a /24); the wildcard mask marks the free host bits (0.0.0.255), which is the form Cisco ACLs and OSPF use.
What if my address is not the start of the block?
The calculator shows the block the address falls in. 192.168.1.77/24 is inside 192.168.1.0/24.