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CIDR Calculator

Calculate CIDR network information including subnet mask, network address, broadcast address, and usable IP ranges

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IP AddressIPv4
CIDR Notation/24

Network Planning Insights

CIDR notation is essential for modern network design, allowing efficient IP address allocation and subnet planning.

❓What is CIDR Calculator

CIDR Calculator is a tool that calculates network information based on CIDR (Classless Inter-Domain Routing) notation. It accepts CIDR format (192.168.1.0/24) and provides subnet details. CIDR is a method for representing IP addresses and network sizes compactly, where the prefix length (/24) indicates the number of network bits. Information calculated: Network address (first IP of subnet), Broadcast address (last IP of subnet), Subnet mask (decimal and binary), Usable IP range (first-last usable), Total IPs (2^host bits), Usable hosts (total - 2), Wildcard mask. Key features: CIDR ↔ subnet mask conversion, Automatic network calculation, IP range display, All notation support, Real-time calculation. Use cases: Network planning (determine subnet sizes), Routing configuration (network routes), IP allocation (identify available IPs), Firewall rules (define network ranges), Subnet design (divide networks), Education (learn CIDR and subnetting). CIDR examples: /24 = 256 IPs, /16 = 65536 IPs, /8 = 16 million IPs. This tool calculates locally in your browser without uploading data.

✨Features

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Complete CIDR Information

Calculate network address, broadcast, usable range from CIDR
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Bidirectional Conversion

Convert between IP/mask and CIDR notation freely
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Subnet Analysis

Detailed subnet statistics and binary representation
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Multiple Formats

Support CIDR, dotted decimal, and binary formats

🎯Application Scenarios

Enterprise Network Planning

Plan and allocate IP subnets for different departments, floors, or locations within an enterprise network. Use CIDR calculator to determine optimal subnet sizes, prevent IP conflicts, and document network topology for IT teams.

Cloud Computing Environments

Plan VPCs and subnets in cloud platforms like AWS, Azure, GCP. Calculate CIDR blocks to allocate private IP space, ensure no overlap between different VPCs, and optimize cloud resource network configuration.

Firewall Rule Configuration

When configuring firewall rules, precise network ranges are needed. Use CIDR calculator to determine IP address ranges to allow or deny, creating accurate access control lists (ACL) and security policies.

Container Network Design

Design networks for container platforms like Docker and Kubernetes. Calculate Pod network CIDR, service network ranges, and node subnets to ensure proper container communication and network isolation configuration.

📚Practical Guide

CIDR Calculation and Subnet Mathematics

CIDR calculator computes network properties from CIDR notation (IP/prefix): network address, broadcast address, subnet mask, wildcard mask, usable host range, and total addresses. Calculations use binary operations. The tool handles prefix validation, IP address validation, and automatic calculations.

Subnet Design and VLSM

CIDR enables VLSM creating subnets of different sizes from single network block. The tool assists subnet planning, calculating required prefix for host count, visualizing IP allocation, and preventing overlaps. Common applications include network design, IP planning, router configuration, and firewall rules.

IPv6 CIDR and Practical Applications

IPv6 CIDR uses 128-bit addresses with /64 standard subnet size. The calculator handles IPv6 notation, prefix delegation, and address planning. Applications include network documentation, troubleshooting, capacity planning, and security. The tool provides both IPv4 and IPv6 calculations.

💬Frequently Asked Questions

❓What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation represents IP address and subnet mask as single value (e.g., 192.168.1.0/24), where /24 indicates mask bits.
💬How to convert subnet mask to CIDR?
Count the number of consecutive 1 bits in subnet mask. For 255.255.255.0 (binary: 24 ones), CIDR is /24. Tool automates this conversion.
🔍What's the difference between /24 and /25?
/24 has 256 IPs (254 usable), /25 has 128 IPs (126 usable). Each increment halves the subnet size. Use calculator to compare.
💡How many usable IPs in /24?
/24 subnet has 256 total IPs, 254 usable (excluding network and broadcast addresses). Tool shows exact calculation for any CIDR.
📚What are private IP ranges?
Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. Tool detects and identifies private addresses automatically.

💡How to Use

1️⃣

IP to CIDR

Enter IP address and subnet mask. Tool converts to CIDR notation. Use for network documentation.
2️⃣

CIDR Analysis

Input CIDR notation (e.g., 192.168.1.0/24). Tool shows all subnet details. Use for network planning.
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Subnet Calculation

Calculate network, broadcast, usable IPs from CIDR. View binary representation. Use for subnet design.
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Network Class Detection

Tool identifies network class (A/B/C/D/E) and address type. Use for IP classification.
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Binary Operations

View IP and mask in binary format. Understand bitwise subnet operations. Use for learning and analysis.

🔗Related Documents

📖RFC 4632 - CIDR NotationCIDR address allocation specification
🌐IPv4 SubnettingIPv4 subnetting guide and calculator
📚RFC 1878 - Subnet TablesIPv4 subnet allocation tables
🔧Subnet Mask ReferenceSubnet mask reference and conversion guide
🏛️IANA Address SpaceOfficial IPv4 address space registry

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