~/tools / CIDR Calculator
CIDR Calculator
Compute the network address, broadcast address, subnet mask, and number of usable hosts from CIDR notation (e.g. 192.168.1.0/24).
Useful for network design on servers and cloud VPCs, splitting VPC subnets, or double-checking firewall rules — quickly see how many IPs a CIDR block covers and its exact range.
# Use Cases
- Checking how many IPs a CIDR block reserves while designing a VPC or subnet
- Figuring out exactly what range a CIDR in a security group or firewall rule actually allows
- Confirming subnets don't overlap before splitting up an existing network
# Usage
- Enter an IP address and prefix length separated by a slash, like "192.168.1.0/24".
- The network address, broadcast address, and more are calculated automatically as you type.
- Usable host count and the first/last host addresses are also listed.
- Network address
- 192.168.1.0
- Broadcast address
- 192.168.1.255
- Subnet mask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- First usable host
- 192.168.1.1
- Last usable host
- 192.168.1.254
- Total addresses
- 256
- Usable hosts
- 254
# FAQ
- What is CIDR?
- A notation ("IP address/prefix length") for describing a range of network addresses. For example, 192.168.1.0/24 covers the 256 addresses from 192.168.1.0 to 192.168.1.255.
- Why is the usable host count "total minus 2"?
- The first address in each subnet is reserved as the network address, and the last as the broadcast address — neither can be assigned to a host.