Subnet Calculator
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Calculator
Adjust values & calculateSubnet Details
Binary & Hex Representation
Common Subnet Reference
Formula
The network address is found by performing a bitwise AND between the IP address and subnet mask. The broadcast address is found by performing a bitwise OR between the network address and the wildcard mask (inverse of subnet mask). Usable hosts = 2^(32-CIDR) - 2 (subtracting network and broadcast addresses). The CIDR prefix length indicates how many leading bits form the network portion.
Last reviewed: December 2025
Worked Examples
Example 1: Standard Home Network (/24)
Example 2: Enterprise Subnet (/26)
Background & Theory
The Subnet Calculator applies the following established principles and formulas. Computers represent all information using binary, a base-2 number system consisting solely of the digits 0 and 1, each called a bit. Because long binary strings are unwieldy, programmers routinely use octal (base 8) and hexadecimal (base 16) as compact shorthand. Converting between bases follows a consistent algorithm: divide the source number repeatedly by the target base, collecting remainders in reverse order. Hexadecimal digits A through F represent the values 10 through 15, allowing a single character to encode four binary bits, making it the preferred notation for memory addresses, color codes, and bytecode. Bitwise operations manipulate individual bits within integers. AND produces a 1 only when both input bits are 1, making it useful for masking. OR produces a 1 when either bit is 1 and is used for combining flags. XOR flips bits that differ, enabling simple toggle logic and efficient swap algorithms. NOT inverts every bit (one's complement), while left and right shifts multiply or divide by powers of two in constant time. Data storage units ascend in binary multiples of 1024: 8 bits form one byte, 1024 bytes form one kibibyte (KiB), 1024 KiB form one mebibyte (MiB), and so forth. Hard-drive manufacturers historically use decimal prefixes (1 KB = 1000 bytes), creating the persistent confusion between binary and decimal interpretations of the same label. The IEC standardized the binary prefixes KiB, MiB, GiB, and TiB in 1998 to resolve this ambiguity. Network bandwidth is measured in bits per second (bps), most commonly megabits per second (Mbps) or gigabits per second (Gbps). A 100 Mbps connection transfers 100 million bits every second, equating to roughly 12.5 megabytes per second. IP subnet masks define network boundaries; CIDR notation appends a prefix length (e.g., /24) to an address, indicating how many leading bits are fixed. A /24 subnet contains 256 addresses with 254 usable hosts. Algorithm efficiency is described using Big-O notation, which characterises the worst-case growth of time or space relative to input size. O(1) is constant, O(log n) is logarithmic (binary search), O(n) is linear, and O(n²) is quadratic. Cryptographic hash functions like SHA-256 produce a fixed 256-bit (32-byte) digest regardless of input length. File compression algorithms exploit statistical redundancy to reduce storage footprint, and compression ratio equals the original file size divided by the compressed size.
History
The history behind the Subnet Calculator traces back through the following developments. The conceptual foundation of modern computing traces back to Charles Babbage, whose Analytical Engine design of 1837 introduced the idea of a general-purpose mechanical computer with separate storage and processing units, including what he called the Store and the Mill. Ada Lovelace wrote what many consider the first algorithm intended for machine execution while annotating a translation of Luigi Menabrea's account of Babbage's work, also recognising the machine's potential to manipulate symbols beyond mere numbers. George Boole published "The Laws of Thought" in 1854, formalising a two-valued algebra of logic that would later map perfectly to electrical circuits. It remained largely a mathematical curiosity until Claude Shannon's landmark 1937 master's thesis demonstrated that Boolean algebra could describe switching circuits, laying the theoretical groundwork for all digital electronics. Shannon's 1948 paper "A Mathematical Theory of Communication" defined the bit as the fundamental unit of information and established information theory as a rigorous discipline. The same year, the transistor was invented at Bell Labs by Bardeen, Brattain, and Shockley, eventually replacing vacuum tubes and enabling miniaturisation at scale. ENIAC, completed in 1945, was one of the first general-purpose electronic computers, occupying 1800 square feet and consuming 150 kilowatts of power while performing roughly 5000 additions per second. The ASCII standard was ratified in 1963, assigning 7-bit codes to 128 characters and enabling interoperability between computers from different manufacturers. Through the 1970s, the microprocessor consolidated an entire CPU onto a single chip; Intel's 4004 in 1971 marked the beginning of this trend. The Apple II launched in 1977 and the IBM PC in 1981 brought computing to homes and offices, triggering a mass-market software industry. Tim Berners-Lee proposed the World Wide Web in 1989 and launched the first website in 1991 at CERN, transforming the internet from an academic and military network into a global information infrastructure. Mobile computing accelerated through the 2000s with smartphones integrating powerful processors, wireless networking, and GPS into pocket-sized devices, extending computation into every facet of daily life and cementing TCP/IP as the universal communications fabric.
Key Features
- Calculate data transfer time for any file size across connection speeds ranging from dial-up to 10Gbps fiber, accounting for protocol overhead and real-world throughput.
- Convert between all storage units (bits, bytes, KB, MB, GB, TB, PB) using both decimal (SI) and binary (IEC) standards to resolve the common confusion between manufacturers and operating systems.
- Compute pixel density (PPI) from screen resolution and physical dimensions, helping users evaluate display sharpness for monitors, phones, and tablets.
- Estimate server rack capacity and RAID configuration outcomes (RAID 0, 1, 5, 6, 10) including usable storage, fault tolerance, and rebuild time.
- Calculate battery life from mAh capacity and device power consumption in milliwatts, with adjustments for screen-on time, background drain, and charge cycle degradation.
- Generate subnet masks, network addresses, broadcast addresses, and host ranges from CIDR notation, supporting both IPv4 and IPv6 planning.
- Quantify the effect of network latency and jitter on real-time applications such as VoIP, gaming, and video conferencing using round-trip time thresholds.
- Estimate monthly cloud infrastructure costs for compute instances, object storage, data egress, and managed databases across major providers.
Frequently Asked Questions
Formula
Network Address = IP AND Subnet Mask; Broadcast = Network OR Wildcard Mask
The network address is found by performing a bitwise AND between the IP address and subnet mask. The broadcast address is found by performing a bitwise OR between the network address and the wildcard mask (inverse of subnet mask). Usable hosts = 2^(32-CIDR) - 2 (subtracting network and broadcast addresses). The CIDR prefix length indicates how many leading bits form the network portion.
Worked Examples
Example 1: Standard Home Network (/24)
Problem: Calculate subnet details for IP 192.168.1.100 with CIDR /24.
Solution: IP: 192.168.1.100\nCIDR: /24 → Subnet Mask: 255.255.255.0\n\nBinary IP: 11000000.10101000.00000001.01100100\nBinary Mask: 11111111.11111111.11111111.00000000\n\nNetwork (AND): 11000000.10101000.00000001.00000000 = 192.168.1.0\nBroadcast (OR wildcard): 192.168.1.255\nWildcard: 0.0.0.255\n\nUsable range: 192.168.1.1 - 192.168.1.254\nTotal hosts: 256, Usable: 254
Result: Network: 192.168.1.0 | Range: .1-.254 | Broadcast: .255 | 254 usable hosts
Example 2: Enterprise Subnet (/26)
Problem: Subnet 10.0.5.67/26 — find the network, broadcast, and usable range.
Solution: IP: 10.0.5.67\nCIDR: /26 → Subnet Mask: 255.255.255.192\nWildcard: 0.0.0.63\n\n67 in binary: 01000011\nMask last octet: 11000000\nAND: 01000000 = 64\n\nNetwork: 10.0.5.64\nBroadcast: 10.0.5.64 + 63 = 10.0.5.127\nFirst host: 10.0.5.65\nLast host: 10.0.5.126\nUsable hosts: 62
Result: Network: 10.0.5.64 | Range: .65-.126 | Broadcast: .127 | 62 usable hosts
Frequently Asked Questions
How do I determine the right subnet size for my network?
To choose the right subnet size, count the number of devices that need IP addresses and select a CIDR prefix that provides enough usable addresses with room for growth. Include all devices: computers, phones, printers, IoT devices, network equipment, and servers. Plan for 50-100% growth beyond current needs. For 10 devices: /28 gives 14 usable addresses. For 25 devices: /27 gives 30 usable addresses. For 50 devices: /26 gives 62 usable addresses. For 100 devices: /25 gives 126 usable addresses. For 200 devices: /24 gives 254 usable addresses. Remember that every subnet loses 2 addresses (network and broadcast), and you may need addresses for the default gateway, DHCP server, DNS server, and other infrastructure. A common mistake is choosing a subnet that exactly matches current needs — always leave headroom. For VLANs in enterprise networks, /24 is the most common choice for general-purpose subnets.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
How do I verify Subnet Calculator's result independently?
The Formula section on this page shows the equation used. You can reproduce the calculation manually or in a spreadsheet using those steps. Compare your answer against the worked examples in the Examples section, which use known reference values so you can confirm the calculator is behaving as expected.
What inputs do I need to use Subnet Calculator accurately?
Each field is labelled with the required unit (metric or imperial). Gather your source values before starting — for example, a weight measurement in kilograms, a distance in metres, or a dollar amount — and enter them exactly as measured. The formula section on this page lists every variable and explains what each represents.
Does Subnet Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy