To calculate a subnet, enter an IP address and CIDR prefix such as 192.168.1.0/24 into the Subnet Calculator. It returns the network address, broadcast address, subnet mask and usable host range.
Follow along with the free Subnet Calculator (CIDR), which runs in your browser, or browse more tools in this category.
How to use the Subnet Calculator (CIDR)
- Enter the IP address.
- Enter the CIDR prefix length.
- Read the network, broadcast, mask and host range.
- Plan your addressing.
Worked example
192.168.1.0/24 has the mask 255.255.255.0, network 192.168.1.0, broadcast 192.168.1.255 and 254 usable hosts from .1 to .254.
Tips and common mistakes
- Usable hosts are 2 to the power of the host bits, minus 2.
- A larger prefix number means a smaller network.
- Keep room for growth when planning subnets.
Frequently asked questions
What is CIDR?
A notation like /24 that says how many bits are the network part of the address.
Why subtract 2 hosts?
One address is the network and one is the broadcast.
Is it private?
Yes.