CIDR Calculator
Derive an IPv4 network range and subnet mask from an address and CIDR prefix length. Use it to understand an address plan, not to discover devices on a network.
- Runs in your browser
- Nothing is uploaded
- No signup; device limits apply
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How to use this tool
Enter a dotted IPv4 address followed by a prefix, such as 192.168.1.0/24. Distinguish the network address from the displayed first and last host values before allocating addresses.
Results and examples
The block 192.168.1.0/24 contains 256 addresses and uses mask 255.255.255.0. Ordinary network/broadcast exclusions should not be blindly applied to special /31 and /32 uses.
Limitations
- The tool does not query routers or check whether an address is in use.
- Point-to-point /31 links and /32 host routes require their own interpretation.
Fields
| Field | Guidance and constraints |
|---|---|
| CIDR (e.g. 192.168.1.0/24) | Check the unit and format displayed beside this field. |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Sources
Frequently asked questions
Are all 256 addresses in a /24 ordinary hosts?
The block 192.168.1.0/24 contains 256 addresses and uses mask 255.255.255.0. Ordinary network/broadcast exclusions should not be blindly applied to special /31 and /32 uses.
Does the output describe my live network?
The tool does not query routers or check whether an address is in use. Point-to-point /31 links and /32 host routes require their own interpretation.
