CIDR & Subnet Calculator: IP Network Planning Tool

Written by AllinPlus Editorial Team, Technical Research & Engineering Board

Published Jul 12, 2026 • Last reviewed: Jul 19, 2026

Architect and troubleshoot IP networks with absolute precision. This CIDR subnet calculator instantly provides broadcast addresses, usable host ranges, and wildcard masks for any IPv4 or IPv6 subnet.

IP address Prefix (CIDR)

Network bits Host bits click a bit to set the prefix boundary

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IPv6 address Prefix length

EUI-64 interface ID generator

MAC address /64 prefix

Base network (CIDR)

Start IP End IP

CIDR blocks (one per line)

IP address

live lookup · leaves your browser

built for allinplus.net/tools · math verified against RFC 4632 (CIDR), RFC 1918 & RFC 6890 (special-purpose ranges)

How to Use

Step 1: Enter your base IP address (e.g., 192.168.1.0).
Step 2: Select your CIDR prefix (e.g., /24) from the dropdown.
Step 3: Review the generated subnet mask, broadcast address, and valid host range.

Example Calculation

Scenario: Calculating the host range for 10.0.0.0/24.

IP Address: 10.0.0.0
CIDR: /24

Result: Usable Hosts: 254. Range: 10.0.0.1 - 10.0.0.254.

A /24 subnet reserves 8 bits for hosts, allowing 256 total addresses. Subtracting the network and broadcast addresses leaves 254 usable IPs.

Frequently Asked Questions

What is CIDR notation?

Classless Inter-Domain Routing (CIDR) notation is a compact representation of an IP address and its associated routing prefix.

Does this tool support IPv6?

Yes, our calculator handles both IPv4 and full IPv6 prefix expansions.

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Want to understand the underlying mechanics of IP allocation and subnet masking? Read our in-depth networking guide.

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