Choose a prefix length from /0 to /32 and this calculator shows the equivalent subnet mask in dotted decimal, the wildcard mask used by many access control lists, the full 32 bit binary representation and the number of addresses and usable hosts in a block of that size. Subnet masks and CIDR prefixes describe the same thing from two angles, and moving between them by hand is a common source of mistakes, so having the exact mask alongside its host count is genuinely useful when planning networks or reading router configs. The binary view makes it clear how many bits belong to the network and how many are left for hosts. Slide or type the prefix and every field updates immediately. All values are computed locally in your browser, with no data leaving your device.
Each prefix from /0 to /32 maps to one dotted decimal mask; for example /24 is 255.255.255.0 and /26 is 255.255.255.192.
The wildcard mask is the bitwise inverse of the subnet mask and is used in tools like access control lists to match address ranges.
Yes, the mask is shown in binary so you can see exactly which bits are network bits and which are host bits.
Choose a prefix length from /0 to /32 and this calculator shows the equivalent subnet mask in dotted decimal, the wildcard mask used by many access control lists, the full 32 bit binary representation and the number of addresses and usable hosts in a block of that size. Subnet masks and CIDR prefixes describe the same thing from two angles, and moving between them by hand is a common source of mistakes, so having the exact mask alongside its host count is genuinely useful when planning networks or reading router configs.
Yes. Subnet Mask Calculator is completely free, with no sign-up and no usage limits.
Yes. Subnet Mask Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Subnet Mask Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.