Turn CIDR notation into a usable range
CIDR notation like 192.168.1.0/24 compactly describes a block of addresses, but you often need the concrete details: the address range, the subnet mask, and the host count. This calculator expands a CIDR block into those values, which is handy for firewall rules, allowlists, and network planning.
How to use it
- Enter a CIDR block.
- Read the address range, subnet mask, and number of hosts.
- Use the range in a rule or plan.
Where it helps
- Writing firewall or access rules that cover a block.
- Defining an allowlist by range rather than listing addresses.
- Planning how to divide address space.
Questions people ask
What does the number after the slash mean? It's how many leading bits are fixed as the network portion — a larger number means a smaller block of addresses.
Is my input stored? No — the calculation runs in your browser.