An interactive Classless Inter-Domain Routing (CIDR) calculator. Translate between CIDR blocks, netmasks, and host counts, plan Variable Length Subnet Mask (VLSM) structures, and aggregate routes.
CIDR Quick Converter
| Property | Value |
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VLSM Subnet Planner
Subnet a base CIDR block into optimal variable-sized subnets based on required hosts.
IP Route Summarization (Supernetting)
Input multiple subnets or IP addresses to calculate the tightest aggregate CIDR block summarizing them.
Key Features of CIDR Calculator & VLSM Planner
- CIDR Block Allocation Determine host sizes and address counts for any slash notation.
- IP Range Extraction Extract precise start and end IP addresses for your subnet block.
- Subnet Mask Matching Find the subnet mask corresponding to your CIDR prefix instantly.
- IPv4 Boundary Checking Validates network boundaries and flags address misalignments.
CIDR Calculator & VLSM Planner Examples
Convert CIDR /24 to IP Range
Analyze the CIDR block 192.168.1.0/24.
Input
192.168.1.0/24Output
Usable IPs: 192.168.1.1 - 192.168.1.254. Total usable hosts: 254.How to Use CIDR Calculator & VLSM Planner
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1. Enter a CIDR Block
Type an IP address with its prefix length (e.g. 192.168.1.0/24) into the CIDR Block field.
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2. Design Subnets or Summarize Routes
Add subnets with required host counts to generate a VLSM plan, or paste routes one per line to summarize them into a supernet.
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3. Review the Plan
See the calculated network address, usable host range, netmask, broadcast address, and subnet details.
Common Use Cases for CIDR Calculator & VLSM Planner
- Router Routing Setups Configure network routing tables and static routes safely.
- Cloud VPC Planning Plan subnet structures and security group blocks inside AWS, GCP, or Azure.
- Firewall IP Blacklisting Define target address ranges to block or allow within security configurations.
The Technical Details
Bitwise binary operations on IPv4 integers run client-side in the browser.
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation represents an IP address and its network prefix together, e.g. 10.0.0.0/8 means the first 8 bits define the network and the remaining 24 bits identify hosts.
What is VLSM?
Variable Length Subnet Masking (VLSM) lets you divide a network block into subnets of different sizes based on each subnet's host requirements, allocating IP space efficiently.
Can I summarize multiple routes into one?
Yes. Paste one route per line into the Summarize Routes section and the tool computes the smallest supernet that covers all the provided blocks.
Is this tool suitable for real-world network planning?
Yes. It calculates all subnet details including broadcast address, wildcard mask, usable IP ranges, and host counts, making it useful for network design, documentation, and study.