IP Subnet Calculator - Calculate Subnets & Host Ranges
Calculate subnetting details for any IP address and mask. Get network address, broadcast address, usable host range, and wildcard mask instantly.
Related guides: What is a subnet mask? and our subnet cheat sheet.
Understanding This Tool
What It Does
Calculate subnet masks, network addresses, and host ranges for any IP address and subnet mask combination. This tool is essential for network administrators planning IP address allocation, subnetting, and network design.
Understanding the Results
- Network Address: The first address in the subnet
- Broadcast Address: The last address in the subnet
- Subnet Mask: Defines the network portion of the address
- CIDR Notation: Compact representation of subnet mask (e.g., /24)
- Usable Hosts: Number of valid addresses available for devices
- First Host IP: Lowest usable IP address
- Last Host IP: Highest usable IP address
- IP Range: Total addresses in the subnet
Common Use Cases
- Network Design: Plan IP address allocation for corporate networks
- VLAN Setup: Create appropriate subnets for virtual LANs
- Server Configuration: Determine network settings for servers and devices
- Network Isolation: Separate traffic using appropriate subnetting
- Cloud Infrastructure: Configure VPC and subnet settings in AWS, Azure, GCP
Pro Tips & Best Practices
- Common Masks: /24 allows 254 hosts, /25 allows 126 hosts, /26 allows 62 hosts
- Reserved Addresses: Network and broadcast addresses cannot be assigned to devices
- Supernetting: Combine multiple subnets using larger network blocks
Frequently Asked Questions
A subnet mask divides an IP address into network and host portions. It determines how many IP addresses are in the subnet and which addresses can communicate directly without routing.
CIDR (Classless Inter-Domain Routing) uses a slash and number (e.g., /24) to indicate how many bits are in the network portion. /24 means 24 bits for network, 8 bits for hosts (254 usable IPs).
Count your devices plus 20-30% growth buffer. Use /24 for up to 254 hosts, /25 for 126, /26 for 62, /27 for 30, /28 for 14, or /29 for 6 hosts. Always account for network and broadcast addresses.
The network address (first IP) identifies the subnet itself. The broadcast address (last IP) sends to all hosts in the subnet. Neither can be assigned to devices - they reduce usable IPs by 2.
No, private IPs (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) only work on local networks. Internet routing ignores private IPs. Use NAT (Network Address Translation) to connect private networks to the internet.
Subnetting divides a large network into smaller segments. Supernetting (CIDR aggregation) combines multiple small networks into one larger block, often used to reduce routing table size.
Frequently Asked Questions
What is a subnet mask?
A subnet mask divides an IP address into network and host portions. It determines how many IP addresses are in the subnet and which addresses can communicate directly without routing.
What does CIDR notation mean?
CIDR (Classless Inter-Domain Routing) uses a slash and number (e.g., /24) to indicate how many bits are in the network portion. /24 means 24 bits for network, 8 bits for hosts (254 usable IPs).
How do I choose the right subnet size?
Count your devices plus 20-30% growth buffer. Use /24 for up to 254 hosts, /25 for 126, /26 for 62, /27 for 30, /28 for 14, or /29 for 6 hosts. Always account for network and broadcast addresses.
What are network and broadcast addresses?
The network address (first IP) identifies the subnet itself. The broadcast address (last IP) sends to all hosts in the subnet. Neither can be assigned to devices - they reduce usable IPs by 2.
Can I use private IP ranges on the internet?
No, private IPs (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) only work on local networks. Internet routing ignores private IPs. Use NAT (Network Address Translation) to connect private networks to the internet.
What's the difference between supernetting and subnetting?
Subnetting divides a large network into smaller segments. Supernetting (CIDR aggregation) combines multiple small networks into one larger block, often used to reduce routing table size.
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