Subnet Calculator

Enter an IPv4 or IPv6 address with a prefix length to see its network, host range and mask, and how the address splits into network bits and host bits. Drag the prefix slider to watch the network grow or shrink. Everything is worked out in your browser.

For example 192.0.2.10/24, 192.0.2.10 255.255.255.0 or 2001:db8::1/64.

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New to subnetting? IP Addresses, Subnets and CIDR explains prefixes and masks, IPv6 Subnetting and Address Planning covers /48, /56 and /64 plans, and Subnet Calculator technical details lists exactly how each value is worked out.