IP Subnet Calculator
IP Subnet Calculator
IP Subnet Calculator – Instantly Calculate Subnet Masks, IP Ranges & Usable Hosts
The IP Subnet Calculator is a powerful tool that helps you divide an IP address into smaller, manageable subnetworks, also known as subnets. Whether you're managing a home network or configuring enterprise-level routing, this calculator makes it easy to determine subnet masks, prefix lengths (CIDR notation), IP ranges, and the number of usable hosts.
What Is a Subnet?
A subnet is a segment of a larger IP network, used to organize and optimize traffic flow. Subnetting breaks one network into multiple logical networks, which improves security, routing efficiency, and performance.
Subnets are used with the Internet Protocol (IP), which forms the foundation of internet communication. IP is part of the TCP/IP suite (Transmission Control Protocol/Internet Protocol), the core framework behind internet data transmission.
Key Concepts of IP Subnetting
IP Address: A unique identifier assigned to every device on a network. It consists of two parts:
- Network prefix (used for routing)
- Host identifier (used to identify individual devices)
Subnet Mask: A 32-bit number that helps define the division between the network and host parts of an IP address. In IPv4, it's usually written in dot-decimal notation (e.g., 255.255.255.0).
CIDR Notation: Modern subnetting uses Classless Inter-Domain Routing (CIDR). CIDR expresses IP addresses with a prefix length (e.g., 192.168.1.0/24), where /24 means the first 24 bits are for the network.
IPv6 Compatibility: While IPv4 is still dominant, IPv6 adoption is steadily increasing. IPv6 uses prefix lengths instead of subnet masks but functions similarly.
Why Use Subnetting?
Subnetting improves:
Common IPv4 Subnet Sizes and Usable Hosts
Here's a quick reference of typical subnet sizes, their corresponding subnet masks, and how many usable IP addresses (hosts) each provides:
| CIDR Prefix | Subnet Mask | Usable Hosts |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 |
| /16 | 255.255.0.0 | 65,534 |
| /24 | 255.255.255.0 | 254 |
| /30 | 255.255.255.252 | 2 |
| /32 | 255.255.255.255 | 0 (single IP) |
For more granular subnetting:
| CIDR | Subnet Mask | Usable Hosts |
|---|---|---|
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /31 | 255.255.255.254 | 0 (used for point-to-point links) |
The calculator automatically provides this information based on the IP and prefix you enter.
From IP Classes to CIDR
Before CIDR, IP addresses were divided into fixed classes:
- Class A: Large networks (/8 to /15)
- Class B: Medium networks (/16 to /23)
- Class C: Small networks (/24 to /30)
CIDR replaced the rigid class-based system and allows more flexible and efficient IP address allocation, which is especially important with limited IPv4 space.
Benefits of Using This IP Subnet Calculator
Whether you're studying networking, preparing for a certification like CCNA, or managing real-world infrastructure, this IP Subnet Calculator makes subnetting easy and accurate.
IP Subnet Calculator – Instantly Calculate Subnet Masks, IP Ranges & Usable Hosts
The IP Subnet Calculator is a powerful tool that helps you divide an IP address into smaller, manageable subnetworks, also known as subnets. Whether you're managing a home network or configuring enterprise-level routing, this calculator makes it easy to determine subnet masks, prefix lengths (CIDR notation), IP ranges, and the number of usable hosts.
What Is a Subnet?
A subnet is a segment of a larger IP network, used to organize and optimize traffic flow. Subnetting breaks one network into multiple logical networks, which improves security, routing efficiency, and performance.
Subnets are used with the Internet Protocol (IP), which forms the foundation of internet communication. IP is part of the TCP/IP suite (Transmission Control Protocol/Internet Protocol), the core framework behind internet data transmission.
Key Concepts of IP Subnetting
IP Address: A unique identifier assigned to every device on a network. It consists of two parts:
- Network prefix (used for routing)
- Host identifier (used to identify individual devices)
Subnet Mask: A 32-bit number that helps define the division between the network and host parts of an IP address. In IPv4, it's usually written in dot-decimal notation (e.g., 255.255.255.0).
CIDR Notation: Modern subnetting uses Classless Inter-Domain Routing (CIDR). CIDR expresses IP addresses with a prefix length (e.g., 192.168.1.0/24), where /24 means the first 24 bits are for the network.
IPv6 Compatibility: While IPv4 is still dominant, IPv6 adoption is steadily increasing. IPv6 uses prefix lengths instead of subnet masks but functions similarly.
Why Use Subnetting?
Subnetting improves:
Common IPv4 Subnet Sizes and Usable Hosts
Here's a quick reference of typical subnet sizes, their corresponding subnet masks, and how many usable IP addresses (hosts) each provides:
| CIDR Prefix | Subnet Mask | Usable Hosts |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 |
| /16 | 255.255.0.0 | 65,534 |
| /24 | 255.255.255.0 | 254 |
| /30 | 255.255.255.252 | 2 |
| /32 | 255.255.255.255 | 0 (single IP) |
For more granular subnetting:
| CIDR | Subnet Mask | Usable Hosts |
|---|---|---|
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /31 | 255.255.255.254 | 0 (used for point-to-point links) |
The calculator automatically provides this information based on the IP and prefix you enter.
From IP Classes to CIDR
Before CIDR, IP addresses were divided into fixed classes:
- Class A: Large networks (/8 to /15)
- Class B: Medium networks (/16 to /23)
- Class C: Small networks (/24 to /30)
CIDR replaced the rigid class-based system and allows more flexible and efficient IP address allocation, which is especially important with limited IPv4 space.
Benefits of Using This IP Subnet Calculator
Whether you're studying networking, preparing for a certification like CCNA, or managing real-world infrastructure, this IP Subnet Calculator makes subnetting easy and accurate.
How to Use the IP Subnet Calculator
Our IP Subnet Calculator is designed to be intuitive and powerful, helping you quickly determine subnet information for both IPv4 and IPv6 addresses. Follow these steps to get the most out of this tool:
Basic IPv4 Subnet Calculation
- Enter an IP Address - Type a valid IPv4 address (e.g., 192.168.1.0) in the IP Address field.
- Select a Subnet Mask - Either:
- Choose a subnet mask from the dropdown (e.g., 255.255.255.0)
- Enter a CIDR prefix in the field (e.g., /24)
- Click "Calculate" - The calculator will instantly display comprehensive subnet information.
IPv6 Subnet Calculation
- Switch to the IPv6 Tab - Click on the "IPv6" tab at the top of the calculator.
- Enter an IPv6 Address - Type a valid IPv6 address (e.g., 2001:db8::) in the address field.
- Enter the Prefix Length - Specify the prefix length (e.g., /64).
- Click "Calculate" - View the IPv6 subnet details, including network range and address count.
Understanding the Results
The calculator provides detailed information about your subnet:
- Network Address - The base address of the subnet
- Broadcast Address - The last address in the subnet (IPv4 only)
- Subnet Mask - In both decimal and binary formats
- Wildcard Mask - Useful for ACL configurations
- First Usable Host - The first IP that can be assigned to a device
- Last Usable Host - The last IP that can be assigned to a device
- Total Hosts - The number of addresses in the subnet
- Usable Hosts - The number of addresses that can be assigned to devices
- CIDR Notation - The network in slash notation
- IP Class - The traditional class of the IP address (A, B, C, etc.)
- Binary Representation - The IP and subnet mask in binary
Advanced Features
- Subnet Division - For IPv4, you can see how a network can be divided into smaller subnets by adjusting the subnet mask.
- Binary Visualization - The calculator shows binary representations to help understand the bit-level operations in subnetting.
- Network Class Information - Learn about the traditional IP class of your network and its characteristics.
Practical Applications
Use the IP Subnet Calculator for:
- Planning network segmentation for security or performance
- Configuring routers, switches, and firewalls
- Setting up VLANs in enterprise networks
- Designing cloud infrastructure with proper IP allocation
- Studying for networking certifications like CCNA, Network+, etc.
- Troubleshooting IP addressing conflicts or issues
Tips for Effective Subnetting
- Plan for growth - Always allocate more IP addresses than currently needed to accommodate future expansion.
- Use VLSM when appropriate - Variable Length Subnet Masking allows different-sized subnets within the same network.
- Document your subnets - Keep records of your subnet allocations to prevent overlaps and conflicts.
- Consider security boundaries - Align subnet boundaries with security zones when possible.
- Use private IP ranges - For internal networks, use private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).
Common Subnet Masks Reference
| CIDR | Subnet Mask | Usable Hosts | Typical Use |
|---|---|---|---|
| /30 | 255.255.255.252 | 2 | Point-to-point links |
| /29 | 255.255.255.248 | 6 | Very small networks |
| /28 | 255.255.255.240 | 14 | Small office/home networks |
| /24 | 255.255.255.0 | 254 | Standard small network |
| /16 | 255.255.0.0 | 65,534 | Large organizations |