IPv4 Subnet Calculator Guide
Work out the network, broadcast, mask and host range for a CIDR block.
A short companion for IPv4 Subnet Calculator: when it is useful, what it expects, and what to check before using the result.
What it does
Given an address and a prefix length, work out the network address, broadcast address, netmask, wildcard mask and usable host range, along with the total and usable host counts.
Use the tool
Open IPv4 Subnet Calculator, add the input the tool asks for, run it, and check the output before using it elsewhere.
Input and output
- Input: text.
- Output: text.
- Category: Network.
Privacy and processing
Processing happens locally in your browser. This tool does not upload the input to ilham.dev.
Questions
Why is the usable host count two less than the total?
The first address in a subnet is the network address and the last is the broadcast address, and neither can be assigned to a host. The exceptions are /31 and /32, which the tool handles separately.
Can it plan a VLSM layout?
Not directly. Use it to check one block at a time, or the range expander to see which CIDR blocks cover an arbitrary range exactly.
Related guide
For broader background, see Network Debugging Notes.