CIDR / Subnet Calculator
Enter an IPv4 address in CIDR notation (e.g. 192.168.1.0/24) and instantly get the network address, broadcast address, subnet mask, and usable host range.
A /24 network has 256 total addresses.
192.168.1.0192.168.1.255255.255.255.00.0.0.255192.168.1.1 – 192.168.1.254254256About the CIDR / Subnet Calculator
CIDR (Classless Inter-Domain Routing) notation packs a subnet mask into a suffix — /24 means the first 24 bits identify the network, leaving 8 bits (256 addresses) for hosts. It replaced the older class-based (A/B/C) system in the 1990s because it lets networks be sized to what's actually needed instead of fixed 8/16/24-bit blocks.
Two addresses in every subnet are reserved and not assignable to hosts: the network address (all host bits zero) identifies the subnet itself, and the broadcast address (all host bits one) sends to every host on it — which is why a /24 has 256 total addresses but only 254 usable ones.
How to use it
- 1Enter an address with a prefix, e.g. 10.0.0.0/22.
- 2Read the calculated network range, mask, and host counts.
- 3Adjust the prefix to see how the range changes live.
Features
- Network address, broadcast address, and subnet mask
- Wildcard mask and total/usable host counts
- First and last usable IP in the range
- Validates malformed input and out-of-range prefixes
Frequently asked questions
What does the /24 in an IP address mean?
It means the first 24 bits of the 32-bit address identify the network, leaving 8 bits for host addresses within that network — 256 total addresses, 254 usable.
Why are there fewer usable hosts than total addresses?
The first address in a subnet (all host bits zero) is the network address, and the last (all host bits one) is the broadcast address — both reserved, not assignable to a host.
What is a wildcard mask?
It's the inverse of a subnet mask, used by some router/firewall configurations (like Cisco ACLs) instead of a standard mask — where the subnet mask has a 0 bit, the wildcard mask has a 1, and vice versa.
Is my IP address sent anywhere?
No. All calculation happens locally in your browser using plain arithmetic on the address — nothing is looked up or transmitted.