What does a CIDR calculation show?

For IPv4 it shows the network and broadcast addresses, masks, usable host range and a 32-bit network/host map. IPv6 mode summarizes compressed and expanded prefixes and address totals.

How are /31 and /32 handled?

A /31 has two usable addresses for point-to-point links per RFC 3021, while a /32 represents one host route.

Is my IP address uploaded?

No. Subnet calculations run locally in the browser and entered addresses are not uploaded.

Subnet Calculator

Derive network, broadcast, host range and masks from CIDR notation — IPv4 and IPv6, all in your browser.

IPv4 CIDR

Address / prefix

Quick Samples

Subnet Details

Network address192.168.1.0

Broadcast address192.168.1.255

Usable host range192.168.1.1 – 192.168.1.254

Subnet mask255.255.255.0

Wildcard mask0.0.0.255

Total addresses256

Usable hosts254

CIDR notation192.168.1.0/24

IP classC

Address typePrivate (RFC 1918)

Common CIDR Ranges

CIDR	Network	Usable range	Usable IPs
/24	192.168.1.0	192.168.1.1 – 192.168.1.254	254
/16	192.168.0.0	192.168.0.1 – 192.168.255.254	65,534
/8	192.0.0.0	192.0.0.1 – 192.255.255.254	16,777,214

Bit Map

11000000101010000000000100000000

Network (24 bits) Host (8 bits)

IPv6 Addressing Explained: Expanding and Compressing Addresses

How IPv6 addresses are structured, the rules behind the :: shorthand and leading-zero omission, and how to canonicalize an address per RFC 5952.

Subnetting Without the Headache: A Practical CIDR Guide

How CIDR notation, subnet masks, network and broadcast addresses actually work — with the /31 and /32 edge cases most people get wrong.

API Mock Server

Define mock REST routes and intercept fetch calls client-side

Bandwidth Calculator

Estimate how long a file takes to transfer at a given connection speed — correctly handling bits vs bytes (Mbps vs MB/s) and SI vs binary size units

Broken Link Checker

Extract http(s) links from pasted HTML and check them via proxy

cURL to Code Converter

Convert cURL commands to code snippets in multiple languages. Parse cURL and generate JavaScript, Python, PHP, and more.

DNS Lookup Tool

Query DNS records and resolve domain names to IP addresses

DNS Propagation Checker

Compare DNS answers from global public resolvers and see propagation consensus instantly