Free tool

Subnet calculator for IPv4 and IPv6

Enter an address with prefix, such as 192.168.10.37/26 or fd00:1234::/48, the calculator shows everything about the network at once. Runs entirely in your browser.

Free, no sign-up
No tracking, no ads
Runs in your browser only

CIDR in one sentence

The number after the slash says how many bits from the front define the network, the rest are the addresses in it. /24 in IPv4 is 256 addresses (254 usable), /64 in IPv6 is 18 quintillion, the usual network for a single device or server.

In IPv4 the first address (network) and the last (broadcast) are not usable, except for /31 and /32. IPv6 has no broadcast.

FAQ

Is my input sent anywhere?

No. The calculator runs entirely in your browser.

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Your own /64 for your server

IPv6 can be added to our KVM servers, with a /64 of its own per server.

View KVM servers