SEOTools.info / Tools / CIDR / Subnet Calculator
CIDR / Subnet Calculator
Enter an IPv4 CIDR block and get the network address, broadcast, netmask, host range and usable host count.
Enter an address with a prefix, e.g. 10.0.0.0/16.
Next step: Number Base Converter →
About the CIDR / Subnet Calculator
Takes an IPv4 CIDR block like 192.168.1.0/24 and works out the network address, broadcast, netmask, usable host range and total addresses — essential for planning subnets and firewall rules.
What this tool checks
- Network and broadcast addresses
- Netmask and usable host range
- Total and usable host counts
Frequently asked questions
What does the /24 mean?
The prefix length — how many bits are the network. /24 = 256 addresses (254 usable); each step changes the size by a power of two.
Why are two addresses unusable?
The first (network) and last (broadcast) address in a block are reserved, so a /24 gives 254 usable hosts.
The full SEO toolkit
Backlinks, rankings, Search Console and more — one free login.