How to use the cidr converter
- Choose direction: CIDR → range, or range → CIDR.
- Enter the input. The tool returns first IP, last IP, total count, and CIDR notation.
- For range → CIDR it finds the minimum spanning prefix.
CIDR Converter
Convert between CIDR notation and subnet details, or convert a subnet mask to prefix length.
Frequently asked questions
How do I convert 192.168.1.0/24 to an IP range?
/24 has 256 addresses. The range is 192.168.1.0 through 192.168.1.255, with usable hosts 192.168.1.1 to 192.168.1.254.
How do I find the smallest CIDR that contains a given range?
Convert both endpoints to binary, find the longest common prefix, then take that prefix as the CIDR. The block size must be a power of 2 and the start must align to it.
Why are some IP ranges not expressible as a single CIDR?
A CIDR block has to start on a boundary that is a multiple of its size. If your range starts in the middle of a block or spans uneven sizes, you need multiple CIDRs.
How does CIDR replace classful addressing?
CIDR removed fixed class A / B / C boundaries and let prefixes have any length from /1 to /32. This unlocked variable-length subnet masking and route aggregation.