Subnet Mask Calculator
Calculate network addresses, subnet masks, and host ranges with CIDR notation support
Network Input
Calculation Results
When to Use Subnet Mask Calculator
Network Planning
Plan and design network infrastructure by calculating required subnet sizes, determining optimal CIDR blocks, and ensuring efficient IP address allocation.
Router Configuration
Configure routers and switches with accurate network parameters, set up static routes, and implement access control lists using calculated wildcard masks.
Network Troubleshooting
Diagnose connectivity issues by verifying subnet configurations, checking if devices are in the same network segment, and validating routing table entries.
Security Planning
Design secure network segments, implement DMZ zones, create firewall rules based on network boundaries, and plan VPN configurations with proper subnetting.
Education & Learning
Learn networking concepts by visualizing binary representations, understanding CIDR notation, and practicing subnetting calculations for certification exams.
Enterprise Networking
Manage large-scale enterprise networks with multiple VLANs, calculate address pools for DHCP scopes, and plan network growth with proper subnet allocation.
Frequently Asked Questions
What is a subnet mask calculator?
A subnet mask calculator is a tool that helps network administrators determine network parameters such as subnet masks, network addresses, broadcast addresses, and host ranges from IP addresses and CIDR notation. It automates complex binary calculations and prevents common subnetting errors.
How do I use CIDR notation?
CIDR notation uses a forward slash followed by a number (e.g., /24) to indicate how many bits are used for the network portion. For example, /24 means the first 24 bits are the network, equivalent to subnet mask 255.255.255.0. Higher numbers mean smaller subnets with fewer hosts.
What is the difference between network and broadcast addresses?
The network address is the first IP in a subnet where all host bits are set to 0, while the broadcast address is the last IP where all host bits are set to 1. These addresses cannot be assigned to hosts and are reserved for network identification and broadcasting respectively.
Is this subnet calculator free to use?
Yes, our subnet mask calculator is completely free to use with no registration required. You can calculate unlimited subnets for your network planning needs. All calculations are performed locally in your browser for privacy and speed.
Can I calculate IPv6 subnets?
This calculator focuses on IPv4 subnets. IPv6 uses a different addressing scheme with 128-bit addresses and typically uses /64 subnets for most networks. IPv6 subnetting is much simpler as address space is abundant, and most networks use standard /64 allocations.
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask, commonly used in Cisco access control lists (ACLs) and routing protocols like OSPF. Where the subnet mask has 1s, the wildcard mask has 0s, and vice versa. For example, subnet mask 255.255.255.0 becomes wildcard mask 0.0.0.255.
How many hosts can each subnet size support?
The number of available hosts depends on the subnet mask. Subtract 2 from the total addresses (for network and broadcast addresses). For example: /24 = 254 hosts, /25 = 126 hosts, /26 = 62 hosts, /27 = 30 hosts, /28 = 14 hosts, /29 = 6 hosts, /30 = 2 hosts.
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