IP Address Block Calculator
Calculate subnet information, CIDR blocks, and IP address ranges for network planning
Network Configuration
Network Information
Results
Subnet Breakdown
| Subnet # | Network Address | Broadcast Address | Host Range | Hosts |
|---|
Understanding IP Addresses & Subnetting
Master network fundamentals, CIDR notation, and subnet calculations
Network Fundamentals
IP Address
Unique identifier for devices on a network (e.g., 192.168.1.1)
CIDR Notation
Compact way to specify network size (/24 = 255.255.255.0)
Subnet Mask
Determines which part is network vs host (255.255.255.0)
Subnetting
Dividing large networks into smaller, manageable subnetworks
Private IP Address Ranges
Class A
Large networks
10.0.0.0/8
16.7M hosts
Class B
Medium networks
172.16.0.0/12
1M hosts
Class C
Small networks
192.168.0.0/16
65K hosts
Common Subnet Sizes
Real-World Networking Applications
How IP calculations help in network design, security, and troubleshooting
Network Design
- • Plan IP address allocation
- • Design hierarchical networks
- • Optimize address space usage
- • Plan for future growth
Security & Isolation
- • Separate network segments
- • Control traffic flow
- • Implement security policies
- • Create DMZ networks
Troubleshooting
- • Diagnose connectivity issues
- • Verify subnet configurations
- • Calculate routing paths
- • Identify IP conflicts
Cloud Networking
- • VPC/VNet configuration
- • Multi-region connectivity
- • Hybrid cloud networks
- • Container networking
BYOD & WiFi
- • Guest network isolation
- • Dynamic IP assignment
- • Mobile device management
- • Bandwidth allocation
Home Networking
- • Router configuration
- • Port forwarding setup
- • IoT device management
- • Network optimization
IP Planning Best Practices
Document Everything
Keep detailed records of IP assignments and network topology
Plan for Growth
Allocate larger subnets than currently needed
Use Consistent Schemes
Develop standard naming and numbering conventions
Avoid Overlap
Prevent IP conflicts in VPN and remote connections
Security First
Isolate sensitive systems with proper subnetting
Test Configurations
Always verify subnet calculations before implementation
Network Planning Considerations
This calculator provides accurate IP and subnet calculations based on CIDR notation. Always consider your specific network requirements, security policies, and future expansion needs when designing networks. For production environments, consult with network professionals and test configurations thoroughly before implementation.
Frequently Asked Questions
Common questions about IP addresses, subnetting, and network planning
What is the difference between CIDR notation and subnet masks?
CIDR notation (like /24) is a shorthand way to express subnet masks. /24 means the first 24 bits are used for the network portion, equivalent to the subnet mask 255.255.255.0. CIDR is more compact and commonly used in modern networking, while subnet masks show the actual binary representation.
How many hosts can I fit in different subnet sizes?
The number of hosts = 2^(32-CIDR) - 2 (subtract 2 for network and broadcast addresses). Common examples: /30 = 2 hosts, /29 = 6 hosts, /28 = 14 hosts, /27 = 30 hosts, /26 = 62 hosts, /25 = 126 hosts, /24 = 254 hosts. Use our calculator above for any CIDR value.
What are private IP addresses and when should I use them?
Private IP addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are reserved for internal networks and cannot be routed over the internet. Use them for internal devices, home networks, and corporate LANs. They provide security through network isolation and allow multiple organizations to use the same addresses.
What's the difference between network, broadcast, and host addresses?
The network address is the first address in a subnet (all host bits are 0) and identifies the subnet itself. The broadcast address is the last address (all host bits are 1) used to send messages to all devices in the subnet. Host addresses are all addresses in between that can be assigned to devices.
How do I choose the right subnet size for my network?
Consider current device count, future growth (plan for 2-3x expansion), security requirements (separate VLANs), and address efficiency. For small offices, /27 or /26 works well. For departments, use /25 or /24. Always leave room for growth and avoid creating subnets that are too small.
Can I use this calculator for IPv6 addresses?
This calculator is designed for IPv4 addresses only. IPv6 uses a completely different addressing scheme with 128-bit addresses instead of 32-bit. IPv6 subnetting works differently and typically uses /64 subnets for end networks. Consider using a dedicated IPv6 calculator for IPv6 network planning.
Real-World Calculation Examples
Practical scenarios showing how to apply IP calculations in common networking situations
Small Office Network (30 devices)
Input: 192.168.1.0/27
Planning for 30 devices with room for growth
💡 Perfect for a small office with computers, printers, and phones. Leaves no unused addresses, maximizing efficiency.
Department Segmentation (250 devices)
Input: 10.1.0.0/24
Large department with workstations, servers, and IoT devices
💡 Standard /24 subnet provides adequate space for a full department while maintaining simple addressing scheme.
Point-to-Point Router Link
Input: 203.0.113.0/30
Connecting two routers with minimal address waste
💡 /30 subnets are perfect for router-to-router connections, using exactly the minimum addresses needed.
Home Network with Guest VLAN
Main Network: 192.168.1.0/26
Family devices, smart home, trusted IoT devices
Guest Network: 192.168.1.64/26
Isolated guest access and untrusted devices
💡 Splitting a /24 network into two /26 subnets provides isolation while maximizing address utilization.