What does this tool do?
The Wildcard Mask Calculator instantly derives the wildcard mask, subnet mask and usable host count from a CIDR prefix (e.g. /26) or a dotted subnet mask. It gives you the exact wildcard value you need when writing Cisco ACLs. Everything is computed in your browser.
How to use it
- Enter an address, domain or value.
- View the results instantly.
- Copy the details you need.
How it works
You enter a CIDR prefix (/24) or a subnet mask (255.255.255.0) and the tool computes the bitwise complement to produce the wildcard mask. For /26, the subnet mask is 255.255.255.192 and the wildcard mask is 0.0.0.63. It also reports the total address count and usable hosts (2^(32-prefix) - 2).
Common use cases
The most frequent use is on Cisco routers and switches for ACLs, OSPF network statements and route-maps, all of which expect a wildcard mask rather than a subnet mask. Network engineers use it to verify the correct wildcard value when summarizing a subnet or matching an IP range.
Frequently asked questions
What is the difference between a wildcard mask and a subnet mask?
A subnet mask uses 1s for network bits and 0s for host bits; a wildcard mask is the exact inverse. In a wildcard mask a 0 bit means 'must match' and a 1 bit means 'don't care', which is the logic Cisco ACLs rely on.
Must a wildcard mask always be contiguous?
No. Subnet masks are contiguous, but wildcard masks in Cisco ACLs can use non-contiguous patterns (e.g. 0.0.255.0) to match specific groups of addresses. This tool produces the standard CIDR complement.
Is Wildcard Mask Calculator free?
Yes. Wildcard Mask Calculator and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. Wildcard Mask Calculator works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.