Network Tools
Convert an IPv4 CIDR prefix into its subnet mask.
Use this Network Mask Calculator to convert CIDR notation like /24 into a dotted decimal subnet mask such as 255.255.255.0. It is useful for subnetting practice, network configuration, and quick IPv4 reference checks.
Use this Network Mask Calculator to convert CIDR notation like /24 into a dotted decimal subnet mask such as 255.255.255.0. It is useful for subnetting practice, network configuration, and quick IPv4 reference checks.
Use network mask calculator when you need a fast browser-based result without extra setup. It works well for quick checks, one-off tasks, and routine formatting or calculation work.
Read step-by-step usage guidance, best practices, and common mistakes.
See common questions and answers about input, output, and tool usage.
Review practical input and output examples before running the tool.
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Input
24
Output
CIDR: /24 Subnet Mask: 255.255.255.0
Converts a common /24 subnet into dotted decimal form.
Input
/30
Output
CIDR: /30 Subnet Mask: 255.255.255.252
Useful for small subnets and point-to-point configurations.
Fix: Enter just the prefix like 24 or /24 for this tool.
Fix: Use a number between 0 and 32.
Fix: This tool is only for IPv4 subnet masks.
It converts an IPv4 CIDR prefix into a dotted decimal subnet mask.
Yes. Both 24 and /24 are accepted.
No. It is only for IPv4 subnet masks.
Many devices, documents, and labs still use dotted decimal subnet masks.
It is 255.255.255.0.