network tool
CIDR Converter
Type a subnet mask to get its CIDR prefix length, or type a prefix length to get the mask. The converter validates that the mask is contiguous and reports the result.
Waiting for files
Accepted input
- A dotted-decimal mask (255.255.255.0), a prefix with slash (/24), or a bare prefix (24).
Limits
- IPv4 only.
- Prefix length must be between 0 and 32.
- Masks must be contiguous (no gaps in the bit pattern).
Local processing
- Conversion runs in your browser. Nothing is uploaded.
How to use CIDR Converter
- Enter a subnet mask or a prefix length.
- Press Convert to see the matching value.
- Copy the result or download the report.
What it does
- Converts both ways: mask to prefix, prefix to mask.
- Validates that the mask is contiguous and reports an error otherwise.
- Accepts /24, 24, or 255.255.255.0 as input.
Limits and things to know
- IPv6 is not supported in this version.
- The tool converts one mask at a time; it does not batch-convert a list.
Example
Reading a firewall rule
A rule mentions /22. Type /22 to see it maps to 255.255.252.0, which covers 1024 addresses.
Frequently asked questions
Why does 255.255.255.1 fail?
It is not a valid subnet mask because the bit pattern is not contiguous. Real subnet masks always have a single block of 1s followed by 0s.
What does /0 mean?
/0 matches every IPv4 address. The mask is 0.0.0.0 and the network contains 4,294,967,296 addresses.
Can I convert several masks at once?
Not yet. Run the converter once per mask. The report keeps the last result only.
Runs entirely in your browser on wifiee.com. Files are never uploaded.