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173 converters across 7 categories — measurement, data, science, and more.

💾Data & Digital44 ⚡Energy & Power4 🏠Everyday25 📏Measurement18 🔢Numbers7 🔬Science68 ⏱️Time & Speed7

Start with your question

What are you trying to convert?

Scaling a recipe for more people?Convert cups to ml, tablespoons to grams, and ounces to kilograms without looking anything up.Cooking Converter →Working with file or disk sizes?Translate between KB, MB, GB, TB — and understand why your OS shows less than the drive label.Data Storage Converter →Building, measuring, or renovating?Switch between metres, feet, inches, and yards for construction or interior planning.Length Converter →Reading a number in a different base?Convert between binary, octal, decimal, and hex — essential for debugging or bitwise work.Number Base Converter →Comparing energy or electricity usage?Convert joules, kilowatt-hours, calories, and BTUs across appliances, diets, and fuel sources.Energy Converter →Dealing with Indian land measurements?Convert between bigha, acre, guntha, cent, and square feet for property buying or legal documents.Land Area Converter →

Things worth knowing

Unit facts that change how you think

1 in = 2.54 cmexact by treaty

The only exact imperial–metric conversion

The inch-to-centimetre relationship is one of the few unit conversions defined as exact, not approximate. Set by international agreement in 1959, it means all other length conversions — feet, yards, miles — are also exact derivations. Most other unit conversions involve rounding at some decimal place.

1 GB ≠ 1 GiBtwo different things

Why your OS shows less storage than the label

Drive manufacturers measure in decimal gigabytes (10⁹ bytes). Operating systems report in binary gibibytes (2³⁰ bytes). A "500 GB" drive appears as ~465 GB in Windows — not a lie, just different number bases. The data converter shows both so you know exactly what you are buying.

−273.15°Cabsolute zero

The floor that no temperature can cross

Absolute zero is the point at which molecular motion theoretically stops. The Kelvin scale starts here, which is why it has no negative values — every temperature above −273.15°C maps to a positive Kelvin number. Scientists use Kelvin precisely because it eliminates negatives from thermodynamic equations.

7 base unitseverything else is derived

All of physics in seven measurements

The International System of Units defines just seven base units: metre, kilogram, second, ampere, kelvin, mole, and candela. Every other unit — the newton, pascal, watt, volt — is a derived combination of these seven. Understanding this makes unit conversion feel less arbitrary and more like algebra.

Frequently Asked Questions

What is the difference between a unit converter and a calculator?

A converter translates a value between units of the same physical quantity — for example, kilometres to miles, or kilograms to pounds. A calculator applies a formula to one or more inputs to produce a derived result — for example, computing the area of a circle from its radius. Converters have a fixed mathematical relationship (the conversion factor); calculators may involve conditional logic or multiple variables.

Are the conversion factors exact or approximate?

Most are exact within the precision displayed. A small number of conversions — particularly those between imperial and metric for legacy units like the BTU or calorie — involve rounded factors that differ slightly across standards bodies. Where a conversion is approximate, the tool notes it. For everyday use the difference is negligible; for scientific or legal work, always verify against the relevant standard.

What is the difference between GB and GiB?

A gigabyte (GB) is 10⁹ bytes (1,000,000,000 bytes) — the definition used by storage manufacturers and most file-transfer specs. A gibibyte (GiB) is 2³⁰ bytes (1,073,741,824 bytes) — the definition used by most operating systems when displaying disk size. A 1 TB drive contains 1,000 GB but only about 931 GiB, which is why the OS shows less than the label.

How do I convert between binary, octal, decimal, and hex?

Use the Number Base Converter — enter your value, select the source base, and the tool outputs the equivalent in all four bases simultaneously. It supports integers of any size and is useful for reading memory addresses, colour hex codes, file permissions, and bitwise operation results.

Can I convert between Indian land units like bigha and acre?

Yes. The Land Area Converter covers bigha, biswa, guntha, cent, marla, kanal, square feet, square metres, and acres. Note that the size of a bigha varies by state in India — the tool lets you select the regional variant (e.g., UP bigha, Bengal bigha) before converting.

Which temperature scale does scientific work use?

Science uses Kelvin (K) because it starts at absolute zero and eliminates negative values from thermodynamic equations. Engineering often uses Celsius or Fahrenheit depending on region. The Rankine scale (°R) is an absolute scale based on Fahrenheit, used in some US engineering contexts. All four are supported in the temperature converter.

Do these converters work offline?

Yes. All conversion logic runs in your browser — no server request is made after the page loads. The tools work offline once the page is cached, which makes them reliable even on slow or intermittent connections.

Can I share a conversion with someone?

Yes. Every converter writes the current value and selected units into the URL in real time. Copy the address bar and share it — the recipient opens the same conversion pre-filled. This is useful for sending specifications, sharing recipe adjustments, or citing a unit for a document.

What unit systems are covered?

The library covers SI (metric), imperial, US customary, and several domain-specific systems — Indian land units, cooking measurements, clothing sizes, data storage (decimal and binary), and scientific units like angstroms and parsecs. If a unit you need is missing, check the category page for the closest available tool.

Is there a converter for Indian number notation (lakh, crore)?

Yes. The Indian Number Converter translates between the Indian numbering system (lakh, crore, arab) and the international system (million, billion, trillion), and also converts numbers to words in both formats — useful for cheques, legal documents, and financial reports.

About this converter library

thecalcu.com brings together over 35 free unit converters across measurement, data, energy, number systems, science, time and speed, and everyday use. Conversion factors follow SI definitions and international standards, with Indian-specific variants for land area and number notation.

Every converter is bidirectional — enter a value in either unit and the other updates instantly. Multi-unit converters (like the length or area tools) show all common units at once so you can scan the equivalents without switching fields. All conversions run in the browser: nothing is sent to a server, inputs are never stored, and the tools work offline once loaded.

The library covers measurement converters for length, weight, area, volume, and temperature; data converters for storage and transfer speed in both decimal (SI) and binary (IEC) prefixes; energy converters spanning joules, kilowatt-hours, and calories; and science converters for pressure, force, density, frequency, and more. Everyday converters handle clothing sizes, cooking measurements, shoe sizes, and fuel efficiency — everything from a kitchen table to an engineering desk.

Measurement converters Data converters Energy converters Number converters Science converters Time & Speed converters Everyday converters

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