CIDR Subnet Calculator

Calculate IPv4/IPv6 ranges, masks, address counts, and subnet containment

IPv4 or IPv6 CIDR

The prefix is optional; IPv4 defaults to /32 and IPv6 to /128. Compressed and IPv4-mapped IPv6 are supported.

IPv4 /24

Address familyIPv4

Normalized address192.168.10.42

Network192.168.10.0/24

Subnet mask255.255.255.0

Wildcard mask0.0.0.255

First usable address192.168.10.1

Last usable address192.168.10.254

Broadcast address192.168.10.255

Total addresses256

Usable addresses254

Reverse DNS42.10.168.192.in-addr.arpa

IPv4 binary

11000000.10101000.00001010.00101010

Subnet containment check

Contained

All parsing and subnet calculation happens locally. IPv4 /31 networks are treated as two usable point-to-point addresses per RFC 3021.

About CIDR Subnet Calculator

Calculate IPv4/IPv6 ranges, masks, address counts, and subnet containment.

No installation is required and input is not permanently stored. Encoding, formatting, image and QR tools run locally in your browser; only network lookups connect to their respective services.