Calculators
IP Subnet Calculator
Calculate the IPv4 network address, broadcast address, usable host range, subnet mask and wildcard from an IP and prefix.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Planning office or cloud network ranges
- Checking whether two addresses share a subnet
- Configuring firewall and router rules
- Studying for networking exams
About this tool
What the IP Subnet Calculator does
An IPv4 subnet is defined by an address and a prefix length such as /24. The prefix sets how many bits identify the network; the rest identify hosts. This calculator works out the network and broadcast addresses, the usable host range and the masks.
Formula
- Block size = 2^(32 − prefix)
- Network = address rounded down to a multiple of the block size
- Broadcast = network + block size − 1
- Usable hosts = block size − 2 (except /31 and /32)
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| IPv4 address | 192.168.10.37 |
| Prefix length | /24 |
| Result | Value |
|---|---|
| Network address | 192.168.10.0/24 |
| Usable hosts | 254 |
| First usable host | 192.168.10.1 |
| Last usable host | 192.168.10.254 |
| Broadcast address | 192.168.10.255 |
| Subnet mask | 255.255.255.0 |
| Wildcard mask | 0.0.0.255 |
| Total addresses | 256 |
How to read the result
A /31 is a special case used for point-to-point links, where both addresses are usable. A /32 identifies a single host.
The wildcard mask is the inverse of the subnet mask and is used in router access lists and some firewall rules.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
256 addresses, of which 254 are usable hosts after excluding the network and broadcast addresses.
A 32-bit value with the network bits set to 1, such as 255.255.255.0 for a /24.
No. This calculator covers IPv4 addresses and prefixes from /8 to /32.
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