All tools
CIDR / Subnet Calculator
Network, broadcast, host range, mask, and contains-check.
Why this exists
IP math comes up constantly, firewall rules, route tables, 'does this client fit in our scope?'. Doing it by hand burns time and invites mistakes.
How to use
- Type a CIDR (e.g. 10.0.1.0/24). The block details appear instantly.
- Optional: type an IP in the second box to check whether it sits inside the block.
- Works for IPv4. For IPv6 ranges, paste the prefix (e.g. fd00:abc::/48).
Worked example
Try 10.0.1.0/24 for a classic /24 LAN, or fd00:abc::/48 for an IPv6 site prefix.