IP Address & Subnet Reference
A complete, calculated IPv4 reference: every subnet mask from /8 to /30, the common private /24 blocks with their usable ranges, and the special addresses every network engineer must know. All values are computed, not estimated.
Subnet masks by prefix
Every CIDR prefix, its dotted-decimal mask, host count and wildcard:
/1 /2 /3 /4 /5 /6 /7 /8 /9 /10 /11 /12 /13 /14 /15 /16 /17 /18 /19 /20 /21 /22 /23 /24 /25 /26 /27 /28 /29 /30 /31 /32
See the printable subnet mask cheat sheet.
Special-purpose addresses
127.0.0.1 0.0.0.0 255.255.255.255 169.254.0.0/16 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16
Calculate any subnet
Need a custom subnet? Our free subnet calculator computes network, broadcast, mask and host range for any address and prefix instantly.
Frequently asked questions
What is a subnet mask?
A subnet mask marks which part of an IP address is the network and which is the host. For example /24 (255.255.255.0) uses 24 network bits and 8 host bits, giving 254 usable hosts.
How do I find the usable range of a subnet?
Take the network address plus 1 as the first host and the broadcast address minus 1 as the last host. Our per-subnet pages and calculator show this for any block.
What are the private IP ranges?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 (RFC 1918). They are used inside private networks and are not routable on the public internet.
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