What is a subnet calculator used for?

A subnet calculator is used to determine network information from an IP address and subnet mask. It calculates the network address, broadcast address, usable IP range, number of available hosts, and helps network administrators plan and organize IP address allocation efficiently.

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its subnet mask. It uses a slash followed by a number (e.g., /24) indicating how many bits are used for the network portion. For example, 192.168.1.0/24 means the first 24 bits are the network address.

How do I calculate the number of usable hosts in a subnet?

The number of usable hosts is calculated using the formula: 2^(32-prefix) - 2. The subtraction of 2 accounts for the network address and broadcast address which cannot be assigned to hosts. For example, a /24 subnet has 2^8 - 2 = 254 usable hosts.

What are private IP address ranges?

Private IP address ranges are reserved for internal networks and include: 10.0.0.0/8 (10.0.0.0 to 10.255.255.255), 172.16.0.0/12 (172.16.0.0 to 172.31.255.255), and 192.168.0.0/16 (192.168.0.0 to 192.168.255.255). These addresses are not routable on the public internet.

Is this subnet calculator really free?

Yes! This subnet calculator is completely free to use with no subscriptions, registrations, or hidden fees. FreeWWW.com provides free tools and utilities for everyone. Calculate unlimited subnets without any cost or limitations.

Free Online Subnet Calculator (No Signup)

About This Tool

This comprehensive subnet calculator helps you understand and calculate IP subnets with ease. Enter an IP address and subnet mask to instantly see network address, broadcast address, usable host range, and binary breakdown. Perfect for network administrators, IT professionals, and anyone learning about networking.

How to Use This Tool

Enter an IP address — Type an IPv4 address (e.g., 192.168.1.0) in the IP Address field
Set the subnet mask — Enter a subnet mask (e.g., 255.255.255.0) or CIDR notation (e.g., /24), or use the slider for quick selection
Use quick presets — Click preset buttons like /8, /16, /24 to jump to common subnet sizes
Review the results — See network address, broadcast address, usable host range, total hosts, and binary breakdown instantly

Common Use Cases

How many usable hosts are in a /24 subnet? Enter any IP with /24 to instantly see the host count, network range, and broadcast address
How do I convert a subnet mask to CIDR notation? Enter the subnet mask (e.g., 255.255.255.128) and the tool shows the equivalent CIDR prefix length
How do I plan subnets for my network? Experiment with different CIDR values to find the right subnet size for your number of hosts and network segments

Network Information

Network Address

Broadcast Address

First Usable Host

Last Usable Host

Subnet Mask

CIDR Notation

Total Hosts

Usable Hosts

Network Class

IP Type

Wildcard Mask

IP Address (Binary)

Host Capacity Visualization

0 hosts

Network & Broadcast (2)

Usable Hosts

Binary Breakdown

Understanding how the subnet mask divides network and host portions:

Subnet Divider

Divide this network into smaller subnets:

Number of Subnets to Create:

🌐 Subnet Calculator