Subnet Mask Calculator

Free Online IP Address Calculator

The Subnet Mask Calculator is a free online tool that instantly calculates network address, broadcast address, and available host count from an IP address and subnet mask. Supports CIDR notation (e.g., /24), ideal for network design, IP management, and troubleshooting. All calculations are performed in your browser for complete privacy.

How to Use

Using the Subnet Mask Calculator is very simple:

Step 1: Enter IP Address
Enter the IP address you want to calculate (e.g., 192.168.1.10). Use IPv4 format (xxx.xxx.xxx.xxx).
Step 2: Select Subnet Mask
Choose a subnet mask from the dropdown list. Both CIDR notation (e.g., /24) and actual mask values (255.255.255.0) are displayed.
Step 3: Click Calculate
Click the "Calculate" button to instantly display network address, broadcast address, host range, and available host count.

Your IP address is never sent to our servers. All calculations are performed in your browser, ensuring complete privacy.

Subnet Mask Calculation

IP Address

Subnet Mask

Practical Use Cases for Subnet Mask Calculator

Subnet mask calculations are used in network management for the following scenarios:

Network Design & Subnetting

When dividing an enterprise network by department, calculate appropriate subnet masks to determine IP address ranges. For example, 200 PCs require /24 (254 hosts), but 500 PCs need /23 (510 hosts).

IP Address Management & Allocation

When assigning dynamic IP addresses with a DHCP server, you need to know the exact available IP range, excluding network and broadcast addresses.

Router & Switch Configuration

When configuring IP addresses on router or Layer 3 switch interfaces, incorrect subnet masks will prevent communication. Verify settings beforehand with this tool.

Network Troubleshooting

When investigating communication issues, verify that IP addresses and subnet masks are correctly configured and that devices belong to the same network segment.

VLSM (Variable Length Subnet Mask) Design

For efficient IP address utilization, calculate information for each subnet when using different subnet masks based on required host count in VLSM design.

What is a Subnet Mask? Basic Knowledge

A subnet mask is a 32-bit number that distinguishes the network portion from the host portion of an IP address. In IPv4 networks, it's used to logically divide (subnet) networks.

Purpose of Subnet Masks

Network Division: Split large networks into smaller units for efficient management
Security Enhancement: Reduce security risks by separating networks
Broadcast Control: Limit broadcast traffic to within subnets
IP Efficiency: Select appropriate subnet sizes based on required host count

What is CIDR Notation?

CIDR (Classless Inter-Domain Routing) notation appends a slash (/) and the number of network bits after an IP address. For example, 192.168.1.0/24 indicates that the first 24 bits are the network portion.

Commonly Used Subnet Masks

/8 (255.0.0.0) - Class A, 16,777,214 hosts
/16 (255.255.0.0) - Class B, 65,534 hosts
/24 (255.255.255.0) - Class C, 254 hosts
/30 (255.255.255.252) - Point-to-point connection, 2 hosts
/32 (255.255.255.255) - Single host, loopback

Benefits of Subnet Mask Calculator

Instant Accurate Calculation

Instantly performs complex subnet calculations that are difficult to calculate manually. Prevents binary conversion errors.

Comprehensive Information Display

Displays all necessary information including network address, broadcast address, host range, and available host count.

CIDR Notation Support

Supports both CIDR notation (e.g., /24) and 255.255.255.0 format, ideal for modern network design.

Completely Free & No Registration

No account registration or fees required. Simply access with your browser and start using immediately.

Offline Operation & Security

All calculations are performed in your browser, and IP address information is never sent to our servers. You can safely calculate confidential network information.

Privacy and Security

Local Processing Guarantee

Your entered IP addresses and subnet masks are never sent to our servers. All calculations are executed in your browser, ensuring network information never leaks externally.

No Tracking

This tool does not record or store user input or calculation results. You can safely calculate your company's internal network information.

Input Validation

Automatically validates IP address format and prevents invalid input. Guarantees accurate calculation results.

Frequently Asked Questions (FAQ)

How many hosts can a /24 subnet mask accommodate?

A /24 (255.255.255.0) subnet mask contains 256 IP addresses, but excluding the network address (first) and broadcast address (last), there are 254 available hosts.

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation appends a slash (/) and the number of network bits after an IP address. Example: 192.168.1.0/24. This allows subnet masks to be expressed concisely.

When is a /30 subnet mask used?

/30 (255.255.255.252) provides 2 available hosts, making it ideal for point-to-point connections between routers. It uses IP addresses efficiently without waste.

Can network and broadcast addresses be used?

No, the network address (first address in subnet) identifies the network itself, and the broadcast address (last address) is for broadcasting to the entire network, so neither can be assigned to hosts.

What's the difference between private and public IP addresses?

Private IP addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are used only within organizations and are not routed on the Internet. Public IP addresses are uniquely identified on the Internet.

What is VLSM?

VLSM (Variable Length Subnet Mask) is a technique that uses different subnet masks for different networks. It allows efficient IP address utilization by selecting optimal masks based on required host count.

Does this tool support IPv6?

Currently only IPv4 is supported. IPv6 uses 128-bit addresses and has a different subnetting approach. IPv6 support is planned for future development.

Can I copy the calculation results?

Yes, calculation results are displayed as text, so you can select and copy them. Use them in your network design documents and documentation.