How to use Subnet Calculator
- 1
Open the Subnet Calculator
Go to tools.slaytic.com and open the Subnet Calculator. No sign-up or account required.
- 2
Enter an address in CIDR notation
Type something like 192.168.1.0/24, combining the address with its prefix length.
- 3
Read the results
Network and broadcast addresses, subnet and wildcard masks, usable host range and total address count are all shown together.
How this works in your browser
Every result comes from bitwise arithmetic on the 32-bit address. The prefix length says how many leading bits identify the network, so the subnet mask is that many ones followed by zeros. ANDing the address with the mask clears the host bits and yields the network address; ORing it with the inverted mask sets them all and yields the broadcast address. The usable range is everything between those two, and the total count is two raised to the number of host bits. The wildcard mask is simply the mask inverted. None of this requires a lookup table, which is why the calculation is instant and why it runs locally with your internal addressing never leaving the browser.
Subnet Calculator vs. traditional online converters
| Feature | Subnet Calculator (in-browser) | Traditional online converters |
|---|---|---|
| File upload required | No - never leaves your device | Yes - file is sent to a server |
| Processing queue | None - starts instantly | Often, especially at peak times |
| Watermark on output | Never | Common on free plans |
| Usage limits | None - free, unlimited use | Often capped per day or file size |
| Works offline once loaded | Yes, for most tools | No - requires a live connection |
| Account required | No | Often, for anything beyond a trial |
Who uses Subnet Calculator
Planning a network
Choose prefix lengths that fit your host counts without wasting address space.
Configuring firewalls and ACLs
Get the exact masks and wildcard masks a device configuration expects.
Troubleshooting connectivity
Confirm whether two addresses actually sit in the same subnet.
Studying for certifications
Check subnetting answers while learning the arithmetic behind them.
Frequently asked questions
What is CIDR notation?
Classless Inter-Domain Routing notation expresses an IP address alongside its network prefix length, indicating how many bits define the network portion of the address.
How many usable hosts does a /24 have?
254 usable host addresses - 256 total addresses minus the network address and broadcast address.
Does this support IPv6?
No, this calculator supports IPv4 addressing and CIDR notation only.
Why are two addresses unusable in every subnet?
Because both are reserved. The first, with all host bits zero, identifies the network itself and is what routing tables refer to. The last, with all host bits one, is the broadcast address that reaches every host at once. Neither can be assigned to a device, which is why a /24 gives 254 usable addresses rather than 256.
What is a wildcard mask for?
It is the subnet mask inverted, and Cisco access control lists and OSPF configurations expect it rather than the mask itself. Deriving it by hand is easy to get wrong under pressure, which is why it is worth having calculated alongside everything else.
How do I choose a prefix length?
Count the hosts you need, add room for growth, then pick the smallest subnet that fits. A /24 holds 254, a /25 holds 126, a /26 holds 62, a /27 holds 30. Halving the prefix by one bit doubles the size, so it is easier to reason in those steps than in raw address counts.
Is anything I enter transmitted?
No. The arithmetic runs entirely in your browser, so internal network addressing is never sent anywhere.