IP Subnet Calculator – IPv4 Subnetting Made Easy
Subnetting is one of the most important skills in computer networking, yet it is often considered confusing by beginners. This IP Subnet Calculator is designed to simplify IPv4 subnetting by instantly calculating network details while also helping you understand how and why those results are derived.
Whether you are a networking student, system administrator, ISP engineer, or preparing for certification exams, this tool helps you plan IP networks efficiently and avoid common addressing mistakes.
What Is Subnetting?
Subnetting is the process of dividing a large IP network into smaller, manageable sub-networks. Each subnet operates as an independent network with its own range of usable IP addresses.
- Efficient utilization of IPv4 addresses
- Reduced broadcast traffic
- Improved network performance
- Better security and isolation
Understanding IPv4 Addressing and CIDR
An IPv4 address consists of 32 bits divided into network and host portions. CIDR (Classless Inter-Domain Routing) notation defines how many bits belong to the network.
| CIDR | Subnet Mask | Usable Hosts |
|---|---|---|
| /24 | 255.255.255.0 | 254 |
| /26 | 255.255.255.192 | 62 |
| /30 | 255.255.255.252 | 2 |
How This Subnet Calculator Works
The subnet calculator processes your IP address and CIDR prefix to determine:
- Network address
- Broadcast address
- First and last usable IP
- Total usable hosts
These values are essential for assigning IP addresses to devices and configuring routers or firewalls.
How to Use the IP Subnet Calculator
- Enter an IPv4 address (example: 192.168.1.10)
- Select the CIDR prefix (example: /24)
- Click the calculate button
- Review the generated subnet details
The output clearly identifies which addresses can be assigned to devices and which are reserved.
Subnetting Example
Input: 10.10.10.5/26
- Subnet Mask: 255.255.255.192
- Network Address: 10.10.10.0
- Broadcast Address: 10.10.10.63
- Usable IP Range: 10.10.10.1 – 10.10.10.62
- Total Hosts: 62
Common Subnetting Mistakes
- Assigning the network address to a device
- Using the broadcast address as a host IP
- Selecting incorrect CIDR for point-to-point links
- Overlapping subnets in large networks
When to Use Different CIDR Prefixes
- /30 – Router-to-router point links
- /29 – Small device groups
- /24 – Standard LAN networks
- /32 – Loopback interfaces
IP Subnet Calculator Tool
Auto-Detect IPv4 / IPv6 Subnet Calculator
Subnet Calculator Interface
Frequently Asked Questions
What is the difference between subnet mask and CIDR?
CIDR is a shorthand representation of the subnet mask that specifies the number of network bits.
How many hosts are available in a /27 subnet?
A /27 subnet provides 30 usable host IP addresses.
Can this calculator be used by ISPs?
Yes, it is suitable for ISP planning, enterprise networks, and learning purposes.
Is this subnet calculator free to use?
Yes, it is completely free.
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