IP Subnet Calculator Developer
Work out network, broadcast, mask and usable host range from CIDR notation.
IP Subnet Calculator is a free online tool that work out network, broadcast, mask and usable host range from CIDR notation. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Developer
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 1
- Works offline
- Yes, after the first visit
About IP Subnet Calculator
IP Subnet Calculator is one of 43 developer tools on DuckyTools, and like all of them it runs entirely inside this page. Work out network, broadcast, mask and usable host range from CIDR notation.
How to use it
- Enter ip address / cidr.
- Results update the moment anything changes.
The one setting
| Setting | What it does | Default |
|---|---|---|
| IP address / CIDR | Free text. | 192.168.1.10/24 |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | IP address / CIDR |
Questions
Why are two addresses unusable in a subnet?
The first is the network address and the last is the broadcast address, neither of which can be assigned to a host. That is why a /24 gives you 254 usable addresses rather than 256.
What about /31 and /32?
A /32 is a single host route. A /31 is a special case defined in RFC 3021 for point-to-point links, where both addresses are usable because there is no need for a broadcast.
Which ranges are private?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16, from RFC 1918. The tool flags which side of that line your address falls on.