CIDR and Subnet Mask Calculator
Enter an IPv4 CIDR value or an IP with a subnet mask to calculate the network, broadcast, wildcard mask, and usable hosts instantly.
| Input Value | |
|---|---|
| CIDR | |
| Subnet Mask | |
| Wildcard Mask | |
| Total Addresses | |
| Usable Hosts | |
| IP / Mask Binary |
- Paste a value like
192.168.10.34/27into the CIDR field and the tool will split the IP address and mask automatically. - If you only have the IP and subnet mask, enter them separately. The mask field accepts dotted decimal masks and plain prefix values.
- If you enter two IPv4 addresses, the tool derives the smallest CIDR block that includes both addresses.
- The page updates automatically as soon as the input is complete, and you can still use “Calculate” if you prefer a manual trigger.
- The result table also shows the binary form of the IP and mask, which is useful when checking bit boundaries.
- Use “Load Example” to test the calculator quickly with a sample /27 subnet.
When would I use this tool?
It is useful when you are configuring routers, firewalls, VPCs, VPNs, or server network interfaces and need to confirm the network, broadcast, and usable host range for a specific CIDR block.
Can I enter only a subnet mask without CIDR notation?
Yes. You can enter a dotted decimal mask such as 255.255.255.0 or a plain prefix length such as 24.
Why are /31 and /32 handled differently?
A /31 subnet is commonly used for point-to-point links, so both addresses are considered usable. A /32 represents a single-host route with no additional host range.
Does this tool support IPv6?
Not in the first version. The current scope is intentionally limited to IPv4 so the validation rules and results remain clear and consistent.
What is a wildcard mask used for?
A wildcard mask is the inverse of the subnet mask. It is commonly used in ACLs, Cisco configuration, and network device rule definitions.
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