About cidr calculator
CIDR notation, such as 192.168.1.0/24, writes a network and its size in one expression. The number after the slash is how many leading bits are the network part.
Example
192.168.1.0/24 has 256 addresses, from 192.168.1.0 to 192.168.1.255. The first is the network address, the last is the broadcast address, leaving 254 for hosts.
Quick sizes
- /32 is one address, /31 two, /30 four.
- /24 is 256 and /16 is 65,536.
- Each bit you remove from the prefix doubles the size.
Runs in your browser
Calculations on this page happen on your device. Nothing you enter is uploaded.
A worked example
10.0.0.0/22 has 1,024 addresses: from 10.0.0.0 to 10.0.3.255, with 1,022 usable hosts. Splitting it into four /24 networks gives 10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/24 and 10.0.3.0/24. Cloud networks such as VPCs are planned using these blocks.
Planning tips
- Choose blocks that do not overlap with other networks you may connect.
- Leave unused space for growth.
- Cloud providers reserve a few addresses in each subnet, so the usable count is a little lower.
