CIDR Calculator
Calculate CIDR notation, subnet masks, IP ranges, and aggregate networks. Essential tool for network administrators and engineers.
| Prefix | Mask | Addresses |
|---|---|---|
| /32 | 255.255.255.255 | 1 |
| /31 | 255.255.255.254 | 2 |
| /30 | 255.255.255.252 | 4 |
| /29 | 255.255.255.248 | 8 |
| /28 | 255.255.255.240 | 16 |
| /27 | 255.255.255.224 | 32 |
| /26 | 255.255.255.192 | 64 |
| /25 | 255.255.255.128 | 128 |
| /24 | 255.255.255.0 | 256 |
| /23 | 255.255.254.0 | 512 |
| /22 | 255.255.252.0 | 1,024 |
| /21 | 255.255.248.0 | 2,048 |
| /20 | 255.255.240.0 | 4,096 |
| /19 | 255.255.224.0 | 8,192 |
| /18 | 255.255.192.0 | 16,384 |
| /17 | 255.255.128.0 | 32,768 |
| /16 | 255.255.0.0 | 65,536 |
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Master CIDR Notation and Subnet Calculations
CIDR (Classless Inter-Domain Routing) is the modern standard for IP address allocation. Our CIDR Calculator helps you convert between CIDR notation and subnet masks, calculate IP ranges, and aggregate networks into supernets. Essential for network planning, firewall configuration, and infrastructure management.
What Is CIDR Notation?
CIDR notation represents IP addresses with their routing prefix (e.g., 192.168.1.0/24). The number after the slash indicates how many bits are used for the network portion. CIDR replaced the old classful addressing system, allowing more flexible allocation of IP addresses and reducing routing table sizes through route aggregation.
CIDR Address Format
IP_Address/Prefix_Length (e.g., 10.0.0.0/8)Why Use This Calculator?
Instant Conversions
Convert between CIDR notation and dotted-decimal subnet masks instantly.
IP Range Analysis
Calculate the exact network range, broadcast address, and usable hosts.
Supernetting
Aggregate multiple networks into efficient supernets for route summarization.
Binary Visualization
See the binary representation to understand how CIDR masking works.
How to Use
Common Applications
Network Planning
Design efficient network architectures with properly sized subnets.
Firewall Configuration
Create accurate CIDR-based rules for security policies.
Route Aggregation
Combine multiple routes into supernets to reduce routing table size.
Cloud Infrastructure
Define VPC subnets and security groups in AWS, Azure, or GCP.
Frequently Asked Questions
/24 means 24 bits are used for the network portion, leaving 8 bits for hosts. This equals a subnet mask of 255.255.255.0 and provides 256 addresses (254 usable hosts).