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 must start on a boundary aligned to its size. If your range begins mid-block or crosses uneven allocations, you'll need multiple CIDRs to cover it.
How does CIDR replace classful addressing?
CIDR ditched the rigid class A/B/C boundaries and let you slice networks any way you wanted — /1 through /32. That flexibility opened the door to variable-length subnet masking and route aggregation, two things that made IP space way less wasteful.