Enter the relevant system or network values to calculate subnet mask from cidr and review the result in plain terms.
Inputs
This topic also has a deeper guide and a printable reference pack, so you can move from the live answer into the method, assumptions, and worked examples without leaving the topic cluster.
A fuller printable subnetting pack covering CIDR, subnet masks, wildcard masks, host counts, and network boundaries with binary-first explanations and quick lookup logic.
A worked-examples pack for decoding prefixes, finding ranges, and planning practical IPv4 subnets from real host requirements rather than memorised tables alone.
These are the main values the calculator uses. Keep the units consistent and, where relevant, match the assumptions explained in the related guide.
Use this page when you want a fast subnet mask from cidr result for system planning, conversion work, or networking checks.
These pages apply the conversion or networking logic shown on the page. Review the wider system context before using the result operationally.
Use the Password Entropy Calculator to work out password entropy for networking, storage, or systems planning.
Use the CIDR from Subnet Mask Calculator to work out cidr from subnet mask for networking, storage, or systems planning.
Use the Wildcard Mask from CIDR Calculator to work out wildcard mask from cidr for networking, storage, or systems planning.
Use the Subnet Host Count Calculator to work out subnet host count for networking, storage, or systems planning.