Subnet Calculator - Free Network Tool
Calculate subnets, mask, and host ranges for IPv4 networks.
Data Privacy & Security
100% Local Processing. Your data never leaves your browser. All calculations are securely executed using client-side JavaScript.
How to Use Subnet Calculator
- Provide an IP address and select the desired subnet mask or CIDR prefix.
- Execute the tool by pressing Enter or clicking Calculate.
- View the generated network dimensions, including total hosts, usable hosts, and wildcard mask.
Tool Limitations & Specs
- Operates exclusively via DOM-level JavaScript without server validation.
- Inputs exceeding standard format lengths will be securely rejected.
- Does not interact with external DNS or ICMP systems.
- Requires HTML5 Canvas and modern browser capabilities.
Frequently Asked Questions
What is a subnet mask?
A subnet mask is a 32-bit number that masks an IP address, dividing it into a network address and a host address for routing purposes.
How does subnetting improve network performance?
Subnetting breaks a large broadcast domain into smaller, manageable networks, reducing broadcast traffic and improving overall speed and security.
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask, primarily used in access control lists (ACLs) and OSPF routing protocols to identify which bits of an IP to match.
Why do we subtract 2 when calculating usable hosts?
In any given subnet, the first IP is reserved as the network identifier, and the final IP is reserved for the broadcast address. The rest are usable.
What is a Class C subnet?
Historically, a Class C subnet uses a default /24 mask (255.255.255.0). Though classful networking is obsolete, the term is still used informally to describe a 254-host network.
Can I use this for VLSM (Variable Length Subnet Masking)?
Yes, by adjusting the CIDR prefix in the input, you can calculate specific VLSM blocks for complex, tiered network architectures.
How are subnets calculated?
Subnets are calculated by converting the IP and mask into binary, performing bitwise AND operations for the network ID, and bitwise OR operations for the broadcast.
Is this calculator secure?
Yes, this tool operates 100% locally. It computes the bitwise calculations directly in your browser without tracking or logging your IP addresses.