CIDR Calculator

API & Web

Calculate IPv4 subnet boundaries and usable host counts.

IPv4 subnet calculator

Network, broadcast, mask and usable host range

Network address

—

Broadcast address

—

Subnet mask

—

Prefix length

—

Usable hosts

—

Address range

—

Use cases

Calculate IPv4 subnet boundaries and usable host counts.

1Check a security-group address range

2Plan a small internal subnet

3Review a route table entry

4Parse URLs, run XPath queries, and inspect HTTP status codes

5Build minimal reproducible HTTP requests for frontend/backend debugging

6Review error codes and API compatibility before release

Guidance

The calculator is IPv4-only and does not aggregate multiple prefixes or calculate IPv6 subnet ranges.

Inspect the components and query parameters of an absolute URL.

Look up the standard meaning of an HTTP response status.

Turn common cURL requests into JavaScript Fetch or Axios code.

Test HTTP APIs directly from the browser.