IP Address & Subnet Mask Calculator

Tool Introduction: IP Subnet Calculator

IP subnet calculator is used to calculate IPv4 subnet information, including network address, broadcast address, subnet mask, usable host range, etc. Supports both CIDR notation and traditional subnet mask format, automatically calculates network parameters.

What is IP Subnet Calculator?

IP subnet calculator is used to calculate subnet information for IPv4 networks, including network address, broadcast address, subnet mask, usable IP range, etc. It's an essential tool for network engineers and system administrators for network planning and configuration.

How to Use

1. Enter an IP address, optionally with CIDR (e.g., 192.168.1.10/24)
2. Or choose CIDR format (e.g., /24) or subnet mask format (e.g., 255.255.255.0)
3. The tool will automatically calculate and display all network information
4. Copy the results or reset the input

Common Use Cases

• Network planning and subnetting
• Server and network device configuration
• Firewall rule configuration
• Network troubleshooting
• IP address allocation management

❓ Frequently Asked Questions FAQ

Q1: What is CIDR?
A: CIDR (Classless Inter-Domain Routing) is a more flexible method for IP address allocation and routing, using slash notation (e.g., /24) to represent subnet masks.

Q2: What's the difference between network address and broadcast address?
A: In conventional prefixes from /0 to /30, the network address has all host bits set to 0 and the broadcast address has them set to 1. They are not assigned to ordinary hosts. /31 point-to-point links and /32 host routes are special cases.

Q3: How to calculate usable hosts?
A: For /0 through /30, usable hosts = total addresses - 2. A /24 therefore has 254 usable hosts. Under RFC 3021 a /31 point-to-point link uses both addresses, while a /32 represents one host route.

Q4: What is wildcard mask?
A: Wildcard mask is the reverse of subnet mask, where 0 bits must match and 1 bits can be anything. Commonly used in Access Control Lists (ACL) and OSPF configuration.

Q5: How to choose the right subnet mask?
A: Choose based on the number of IP addresses needed. For example, if you need 100 host addresses, you can choose /25 (126 usable IPs) or /24 (254 usable IPs).

🎯 Key Features

• Real-time Calculation: Instant calculation as you type
• Flexible Input: Paste IP/CIDR together or use separate CIDR and subnet-mask fields
• Quick Prefixes: Apply common /8 through /32 presets with one click
• Complete Information: Displays all critical information including network address, broadcast address, mask, IP range
• Binary Display: Shows subnet mask in binary format for better understanding
• Common Subnets Table: Provides quick reference for common subnets
• One-Click Copy: Copy an individual value or the complete calculation

📖 Usage Examples

Example 1: Home Network

Input:

• IP Address: 192.168.1.1
• CIDR: /24

Output:

• Network Address: 192.168.1.0
• Broadcast Address: 192.168.1.255
• Subnet Mask: 255.255.255.0
• Usable Hosts: 254
• IP Range: 192.168.1.1 - 192.168.1.254

Example 2: RFC 3021 Point-to-Point Link

Input:

• IP Address: 10.0.0.10/31

Output:

• Network Address: 10.0.0.10
• Broadcast/second endpoint: 10.0.0.11
• Subnet Mask: 255.255.255.254
• Usable Hosts: 2
• IP Range: 10.0.0.10 - 10.0.0.11

Common CIDR Reference