CIDR calculator — subnets, ranges and masks
Enter a CIDR block and get the network address, broadcast, usable host range, netmask and host count. It calculates in your browser (0 uploads, works offline).
How to use it
- Enter your input above.
- The result appears live on your device.
- Copy or Download it.
FAQ
How do I calculate a subnet from CIDR notation for free?
Enter a block like 192.168.1.0/24 and the network address, broadcast, first and last usable host, netmask, wildcard and host count appear instantly in your browser with no upload. A host address is normalised to its network automatically.
What does /24 mean?
The number after the slash is how many bits are the network portion. /24 means the first 24 bits (three octets) are the network, leaving 8 bits — 256 addresses, 254 usable — for hosts. Smaller numbers mean bigger networks.
Is anything uploaded?
No. The calculation is local and nothing is stored; it works offline.
Does it handle /31 and /30?
Yes — /31 (point-to-point) and /30 are computed correctly, including their special usable-host counts.
Limits
IPv4 only. IPv6 subnetting is a future addition.
Related
The URL parser decomposes URLs; other developer tools cover encoding and hashing.
Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.