Back to Tools
Subnet (CIDR) Calculator
Calculate network details for IPv4 and IPv6 subnets, including netmask, broadcast address, and host ranges.
Local-First Verification
This Subnet Calculator runs entirely in your browser. All calculations happen locally on your device.
- ✔ No data sent to server (Check DevTools Network tab)
- ✔ Zero-Log policy (We don't even have a database)
- ✔ Works 100% offline
What is CIDR?
Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and for IP routing. The CIDR notation specifies an IP address, a slash ('/') character, and a decimal number. The decimal number is the count of leading 1 bits in the routing prefix mask.