ToolPatch

One page. One job. Done.

← Back to all tools
Network

Wildcard Mask Calculator

Convert subnet masks into wildcard masks for ACL rules.

Last validated: 2026-02-14

Use this free online Wildcard Mask Calculator to convert subnet masks to wildcard masks for ACL and network policy use. Use it for network planning, troubleshooting, documentation, and change review before updating live infrastructure. The form focuses on Subnet Mask and returns Wildcard Mask Input, Result, so you can move from input to answer without setting up a spreadsheet or custom script. Run one realistic example, adjust the inputs, and compare how the result changes before you copy or share it. Treat the output as a planning and diagnostics aid, then verify it against live devices, provider rules, and authoritative DNS or routing data.

Permalink

Input Pattern

Enter values in the left panel, keep units explicit, run the calculation, then copy or share the result. Invalid fields are highlighted immediately.

Wildcard Mask Input

Result

Wildcard mask: 0.0.0.255

Mask bits: 11111111.11111111.11111111.00000000

Wildcard bits: 00000000.00000000.00000000.11111111

How to use this tool

  1. Enter Subnet Mask for the wildcard mask calculator, keeping units, dates, or text format consistent with the form labels.
  2. Confirm address formats, masks, ports, or hostnames match the network environment you are checking.
  3. Click "Run the tool" and review Wildcard Mask Input, Result for the primary output.
  4. Compare the output with device, provider, or DNS authority settings before applying a live network change.

Worked Example

Auto-generated from the tool's current default or entered inputs.

Example Inputs

  • Subnet mask: 255.255.255.0
  • Wildcard mask: 0.0.0.255
  • Binary mask: 11111111.11111111.11111111.00000000
  • Binary wildcard: 00000000.00000000.00000000.11111111

Expected Outputs

Interpretation

Formula References

Assumptions

Explore more versions

Tailored guides for specific audiences, regions, and scenarios.

core

Wildcard Mask Calculator

 geo

Wildcard Mask Calculator for Germany

 geo

Wildcard Mask Calculator for United Kingdom

 geo

Wildcard Mask Calculator for United States

Firewall and ACL resources

Promote network security tools, ACL references, and certification labs.

Sponsored