CodeNimbleToolsFree Online Developer Tools
Explore tools

IP Subnet Calculator

Full IPv4 subnet report from any IP + netmask or prefix — including binary and hex representations.

Tool input is processed locally in your browser and is not submitted to CodeNimbleTools. Avoid pasting production secrets into any device or website you do not fully trust.

Subnet report

Enter an IP and netmask to get the full subnet report, including binary and hex forms.

About this tool

Give it an IP and a mask — as dotted decimal (255.255.255.0) or prefix (/24) — and get the complete subnet picture: network, broadcast, usable range, host counts, wildcard mask, IP classification, plus binary and hexadecimal forms for the bit-level view.

Non-contiguous masks are rejected with a clear explanation, catching a classic configuration typo.

How to use it

  1. Enter the IP address (e.g. 10.0.5.20).
  2. Enter the netmask as dotted decimal or a /prefix.
  3. Read the full report, including binary IP and netmask.
  4. Copy values into your network documentation.

Useful ways to apply it

  • Configuring static IPs with the right mask and gateway range.
  • Verifying VLAN subnet boundaries.
  • Studying for networking certifications (binary view included).
  • Diagnosing "same subnet?" connectivity questions.

Worked example

Example input

10.0.5.20 / 255.255.255.0

Expected output

Network 10.0.5.0/24; broadcast 10.0.5.255

Edge cases to check

  • Non-contiguous masks are not ordinary CIDR masks.
  • /31 and /32 host assumptions differ from traditional worksheets.
  • Cloud platforms may reserve extra addresses.

Known limitations

Results are IPv4 subnet arithmetic, not a guarantee of which addresses a particular platform lets you assign.

How this tool was reviewed

Reviewed with common masks, boundary addresses and /31-/32 caveats.

Last reviewed: September 3, 2026 · Maintainer: William

Standards and technical references

See the site-wide testing methodology for fixture categories, privacy checks and correction policy.

Frequently asked questions

Dotted mask or prefix — which should I enter?
Either. 255.255.255.0 and /24 are identical; the calculator accepts both and shows the other form in the report.
What is a non-contiguous mask?
A mask whose binary form mixes 1s after 0s (like 255.0.255.0). These are invalid for subnetting and the calculator rejects them explicitly.
IPv6 support?
This tool is IPv4-only for now.

Privacy

Tool input is processed locally in your browser and is not submitted to CodeNimbleTools. Avoid pasting production secrets into any device or website you do not fully trust.