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Subnet & Wildcard Mask Converter

Convert between IPv4 prefix lengths, contiguous subnet masks, and inverse wildcard masks. Work locally without uploading network information.

Runs entirely on your deviceNo uploads, accounts, cookies, or personal tracking.

Convert mask

Local processing · no input storage

Network tools
Select the format or assumption to use.
Examples: /24, 255.255.255.0, or 0.0.0.255. Select the matching input format.

Non-contiguous ACL wildcard masks are valid in some systems but cannot be converted to one CIDR and are rejected here.

Enter your data, then select convert mask.
1. Add your data

Enter your network data or load the worked example.

2. Choose the result

Convert mask and review the result and assumptions.

3. Save it locally

Copy the result or download it for your engineering workflow.

About this tool

Use Subnet & Wildcard Mask Converter without an upload

Convert between IPv4 prefix lengths, contiguous subnet masks, and inverse wildcard masks. Work locally without uploading network information.

The operation runs in the current browser tab. Tool input is not included in aggregate analytics, and the standalone download makes no analytics requests.

Network toolsDeveloper tools