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Free IP Subnet Calculator

Calculate network addresses, subnet masks, usable IP ranges, and split subnets instantly. Complete subnet calculator with CIDR notation and binary conversion.

IP Subnet Calculator
Calculate network information from IP address and CIDR notation
/
Network Address
192.168.1.0/24
Usable Hosts
254
IP Class
Class CPrivate

Network Information

Network Address:192.168.1.0
Broadcast Address:192.168.1.255
Subnet Mask:255.255.255.0
Wildcard Mask:0.0.0.255

Usable IP Range

First Usable IP:192.168.1.1
Last Usable IP:192.168.1.254
Total Hosts:256
Usable Hosts:254
Binary Representation
View network calculations in binary format
IP Address
11000000.10101000.00000001.00000000
Subnet Mask
11111111.11111111.11111111.00000000
Network Address
11000000.10101000.00000001.00000000

Network address is calculated using bitwise AND operation between IP address and subnet mask

About Subnet Calculation
  • CIDR notation uses a slash followed by the number of network bits (e.g., /24)
  • The subnet mask determines which portion of the IP address is the network and which is the host
  • Network address is the first address in a subnet (all host bits are 0)
  • Broadcast address is the last address in a subnet (all host bits are 1)
  • Usable IP range excludes network and broadcast addresses (except /31 and /32)
  • All calculations are performed locally in your browser—no data is sent to servers

What Is a Subnet Calculator and Why Do You Need It?

An IP subnet calculator is an essential networking tool that computes network addresses, subnet masks, broadcast addresses, and usable IP ranges from CIDR notation. Our free subnet calculator instantly calculates all subnet information you need for network planning, configuration, and troubleshooting.

IP subnetting is the practice of dividing a network into smaller, more manageable sub-networks (subnets). A subnet calculator automates the complex binary math required to determine network boundaries, available hosts, and address ranges. Network administrators, system engineers, and IT professionals use subnet calculators daily to plan IP address allocation, configure routers and firewalls, design network topologies, and troubleshoot connectivity issues.

CIDR notation explained: CIDR (Classless Inter-Domain Routing) notation expresses IP addresses with a slash followed by the number of network bits. For example, 192.168.1.0/24 means the first 24 bits identify the network, leaving 8 bits for hosts. This provides 256 total addresses (28), with 254 usable for devices after excluding the network address (192.168.1.0) and broadcast address (192.168.1.255).

Real-world example: You receive the IP block 10.50.0.0/16 for your office network. Our subnet calculator instantly tells you: network address is 10.50.0.0, broadcast is 10.50.255.255, you have 65,536 total IP addresses with 65,534 usable for devices, the subnet mask is 255.255.0.0, and your usable IP range is 10.50.0.1 to 10.50.255.254. This information is critical for configuring DHCP servers, routing tables, and firewall rules.

Subnet splitting made easy: Need to divide a /24 network into four separate subnets for different departments? Our subnet split tool calculates all the subnet boundaries automatically. Simply enter your network (like 192.168.1.0/24) and the new CIDR prefix (like /26), and instantly see all four subnets: 192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, and 192.168.1.192/26—each with 62 usable IP addresses. Export results to CSV for documentation and configuration management.

Binary visualization for learning: Understanding subnet calculations requires knowledge of binary operations. Our tool displays IP addresses, subnet masks, and network addresses in both decimal and binary formats, showing exactly how the bitwise AND operation produces the network address. This educational feature helps network students and certification candidates (CCNA, Network+, etc.) master subnetting concepts with visual, step-by-step explanations.

Private vs. public IP detection: The calculator automatically identifies whether your IP address falls in a private range (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) or is publicly routable. It also shows the traditional IP class (A, B, C, D, or E) for educational and legacy system compatibility purposes, though modern networks use classless CIDR notation exclusively.

Powerful IP Subnet Calculator Features

Instant CIDR Calculation

Enter any IP address and CIDR prefix (0-32) to instantly calculate network address, broadcast, subnet mask, and usable host range.

100% Private & Secure

All subnet calculations happen in your browser using JavaScript. No server uploads, no logging, complete privacy.

Subnet Splitting Tool

Divide a network into smaller subnets by specifying a new CIDR prefix. See all subnet boundaries with one click.

Binary Representation

View IP addresses, subnet masks, and network addresses in binary format to understand bitwise operations and subnet math.

Network Class Detection

Automatically identifies IP class (A, B, C, D, E) and private vs. public address space for legacy and security analysis.

Detailed Host Information

Shows total hosts, usable hosts, first usable IP, last usable IP, and percentage of address space used.

Wildcard Mask Calculation

Computes wildcard masks (inverse masks) for Cisco ACL and OSPF configurations automatically.

CSV Export

Export subnet split results to CSV format for easy import into spreadsheets, IPAM systems, and documentation tools.

Sample Networks

Test with pre-loaded examples: Class A, B, C private networks, and small subnets for quick learning and validation.

How to Use the IP Subnet Calculator

  1. 1
    Enter IP address and CIDR

    Type any IPv4 address (like 192.168.1.0) and CIDR prefix (0-32, like /24) in the input fields. Use sample buttons to load common examples.

  2. 2
    View network information

    Instantly see network address, broadcast address, subnet mask, wildcard mask, first/last usable IPs, and total usable hosts.

  3. 3
    Check binary representation

    Scroll down to see binary format of IP, subnet mask, and network address. Understand how bitwise AND calculates the network.

  4. 4
    Split subnets (optional)

    Switch to "Split Subnet" tab. Enter original CIDR and new (larger) CIDR to divide network into smaller subnets. See all subnet ranges.

  5. 5
    Copy and export results

    Click Copy buttons to copy network addresses to clipboard. Export subnet split results to CSV for documentation and configuration.

Common Subnet Masks: CIDR vs. Decimal Notation

CIDRSubnet MaskWildcard MaskTotal HostsUsable Hosts
/8255.0.0.00.255.255.25516,777,21616,777,214
/16255.255.0.00.0.255.25565,53665,534
/24255.255.255.00.0.0.255256254
/25255.255.255.1280.0.0.127128126
/26255.255.255.1920.0.0.636462
/27255.255.255.2240.0.0.313230
/28255.255.255.2400.0.0.151614
/30255.255.255.2520.0.0.342

Benefits and Limitations of Subnet Calculators

Pros

  • Eliminates manual binary math: No need for error-prone calculations—instant, accurate results every time
  • Saves time: Calculate complex subnets in seconds instead of minutes with pen and paper
  • Educational value: Binary visualization helps students learn subnetting concepts and pass networking certifications
  • Network planning: Essential for designing IP address schemes, VLAN allocation, and multi-site deployments
  • Troubleshooting aid: Quickly verify if an IP belongs to a subnet or identify misconfigured subnet masks
  • Documentation: Export subnet lists to CSV for network diagrams, IPAM systems, and configuration management
  • Supports all prefix lengths: Calculate anything from /0 (entire internet) to /32 (single host)
  • Private IP detection: Automatically identifies RFC 1918 private addresses for security and NAT planning

Cons

  • IPv4 only: This calculator works with IPv4 addresses. IPv6 uses different notation and much larger address spaces
  • Requires basic networking knowledge: Users should understand CIDR notation, subnet masks, and network/host bits
  • No automatic VLSM design: Calculator computes subnets but does not auto-design Variable Length Subnet Masks for complex requirements
  • Large subnet splits limited: Displaying millions of subnets (like splitting /8 to /24) is capped at 256 results for performance
  • No IP conflict detection: Calculator cannot check if calculated subnets overlap with existing network allocations

Frequently Asked Questions About IP Subnet Calculators

What is an IP subnet calculator and how does it work?

An IP subnet calculator is a tool that computes network information from an IP address and CIDR prefix. It performs bitwise AND operations between the IP and subnet mask to determine the network address, then calculates the broadcast address, usable IP range, and host count. Our calculator uses JavaScript to run all calculations locally in your browser without sending data to servers.

How do I calculate a subnet mask from CIDR notation?

CIDR notation (like /24) specifies the number of network bits. To convert to a subnet mask: create a 32-bit binary number with that many 1s followed by 0s, then convert to decimal. For /24: 11111111.11111111.11111111.00000000 becomes 255.255.255.0. Our calculator does this instantly—just enter the CIDR prefix and see the subnet mask, wildcard mask, and all network details.

What is the difference between network address and broadcast address?

The network address is the first IP in a subnet with all host bits set to 0 (e.g., 192.168.1.0 in 192.168.1.0/24). It identifies the subnet itself and cannot be assigned to devices. The broadcast address is the last IP with all host bits set to 1 (e.g., 192.168.1.255), used to send packets to all hosts on the subnet. Both are reserved, so usable IPs are between these two addresses.

How many usable IP addresses are in a /24 subnet?

A /24 subnet has 256 total IP addresses (2^8 host bits), but only 254 are usable for devices. The first address is the network address (192.168.1.0) and the last is the broadcast address (192.168.1.255), both reserved. Usable IPs are 192.168.1.1 through 192.168.1.254. Exception: /31 subnets (used for point-to-point links) have 2 usable IPs, and /32 represents a single host.

What are private IP address ranges?

Private IP addresses (RFC 1918) are reserved for internal networks and not routable on the public internet: 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). Organizations use these internally with NAT for internet access. Our calculator automatically detects if your IP is private or public.

How do I split a subnet into smaller subnets?

To split a subnet, increase the CIDR prefix (borrow more host bits for the network). For example, splitting 192.168.1.0/24 into 4 subnets requires /26 (2 more bits = 2^2 = 4 subnets). Use our "Split Subnet" tab: enter the original network and new CIDR, and see all subnet ranges instantly. Each /26 subnet provides 62 usable IPs. Export results to CSV for easy network documentation.

What is a wildcard mask and when is it used?

A wildcard mask is the inverse of a subnet mask, used in Cisco IOS ACLs and OSPF network statements. For subnet mask 255.255.255.0, the wildcard is 0.0.0.255. In ACLs, 0 bits mean "must match exactly" and 1 bits mean "any value accepted." Example: ACL entry "192.168.1.0 0.0.0.255" matches all IPs in the 192.168.1.0/24 subnet. Our calculator shows wildcard masks automatically.

Can I use this subnet calculator offline?

Yes! After the page loads once, all subnet calculations run locally in your browser using JavaScript. You can bookmark the page and use it without an internet connection—no server communication required. This makes it perfect for network engineers working in data centers, remote sites, or secure environments without internet access.

What is the difference between classful and classless addressing?

Classful addressing (obsolete) divided IPs into fixed classes: Class A (/8), B (/16), and C (/24). This was wasteful—a company needing 300 IPs got a Class B with 65,534 addresses. Classless addressing (CIDR) allows any prefix length (/0 to /32), enabling efficient allocation like /23 (512 IPs) or /27 (32 IPs). Modern networks use CIDR exclusively. Our calculator shows both class (for reference) and CIDR notation.

How do I calculate subnets for VLSM (Variable Length Subnet Masking)?

VLSM allows different subnet sizes within the same network. Process: (1) List all subnets needed, sorted by size descending. (2) Allocate the largest subnet first from your address space. (3) Use our calculator to find the network address and next available IP. (4) Repeat for each subnet. Example: From 192.168.1.0/24, allocate /26 (62 hosts), then /27 (30 hosts), then /28 (14 hosts), ensuring no overlaps.

What does the binary representation show?

Binary representation shows IP addresses, subnet masks, and network addresses as 32-bit binary numbers (8 bits per octet). This reveals how subnet calculations work: the network address is the bitwise AND of the IP and subnet mask. For example, 192.168.1.100 (11000000.10101000.00000001.01100100) AND 255.255.255.0 (11111111.11111111.11111111.00000000) = 192.168.1.0. This visualization helps understand subnetting for exams like CCNA.

Is this subnet calculator suitable for IPv6?

No, this calculator is designed for IPv4 only. IPv6 uses 128-bit addresses with hexadecimal notation and completely different subnetting rules. IPv6 networks typically use /64 for subnets (not variable like IPv4), and address planning focuses on hierarchy and aggregation rather than conservation. For IPv6, you would need a specialized IPv6 subnet calculator that handles the larger address space and different prefix allocation standards.

Free IP Subnet Calculator - CIDR & Network Calculator Tool