CIDR ↔ Subnet Mask Converter
Convert a /0–/32 CIDR prefix or a contiguous IPv4 subnet mask.
Processed locally — your input stays in this browser.
Examples and edge notes
IPv4 input uses decimal octets only. Leading zeros are interpreted as decimal and canonicalized without leading zeros. CIDR supports /0 through /32; subnet masks must have contiguous one bits followed by zero bits.
About CIDR ↔ Subnet Mask Converter
Convert an IPv4 CIDR prefix length to a contiguous subnet mask and back.
How to use it
Enter the requested value, review it for accuracy, then run the tool. Read the labeled result fields before copying or using them in another workflow.
Understanding the result
The result presents the values returned or calculated for this specific request. Labels and status messages distinguish successful data, empty results, validation problems, and network errors.
Limitations and privacy
Results are calculated from the values you provide and should be verified against your network requirements before operational changes. Runs locally in your browser; the value you enter is not sent to the Network Tools API.