Santekno/tools
CategoriesTutorials

CIDR / Subnet Calculator

Calculate IPv4 and IPv6 subnet details: network, broadcast, netmask, usable hosts.

Processed in your browserUpdated · Jan 2026
CIDR
0 chars
Subnet details
0 chars

How to use CIDR / Subnet Calculator

Paste your input on the left, choose the options you want, and the output appears instantly on the right. Everything runs in your browser — none of your data is sent to a server.

  • Paste or type your input in the INPUT panel
  • The output regenerates automatically as you type
  • Use Copy to put the result in your clipboard
  • Click Sample to load a working example

What is CIDR / Subnet Calculator?

Enter any IP address in CIDR notation (e.g. 192.168.1.0/24 or 2001:db8::/32) and instantly see the network address, broadcast address, netmask, wildcard mask, usable host range, and total addresses. Useful for network planning, firewall rules, and AWS VPC design. All math runs in your browser. This tool is part of santekno's developer toolbox — a curated collection of utilities built for engineers who care about speed, privacy, and simplicity.

Common use cases

  • Debugging API payloads and integration issues
  • Inspecting tokens, hashes, or encoded strings during development
  • Generating fixtures and sample data for tests
  • Sharing readable output with teammates in code reviews

FAQ

CIDR (Classless Inter-Domain Routing) writes IP + prefix length, e.g. 192.168.1.0/24 means the first 24 bits are the network.