# Unit Converter Convert length, weight, temperature, volume, and dozens of other measurement units instantly with this free online converter tool. --- - **Canonical URL:** https://dothecalculation.com/calculators/unit-converter - **Category:** Everyday utilities - **Publisher:** Do The Calculation (https://dothecalculation.com) - **Cost:** Free, no account or sign-up required - **Privacy:** Runs entirely in the browser; inputs are never sent to a server - **Methodology:** https://dothecalculation.com/methodology --- ## Convert length, weight, and temperature Convert metric and imperial units of length, weight, and temperature instantly. - Length conversions (m, ft, in, km) - Weight conversions (kg, lb, g, oz) - Temperature conversions (C, F, K) ## Metric and Imperial Conversions Different systems of measurement are used globally, with the metric system dominant in science and international trade, and the imperial system used in the United States and other regions. This converter translates values between common units by converting through a standard base unit (meters for length, grams for weight) or using direct temperature formulas. The core conversion logic is: $$\text{Target Unit} = \text{Source Unit} \times \text{Conversion Factor}$$ ## Temperature Scale Mathematics Unlike length and weight, which scale proportionally from zero, temperature scales have different starting points (offsets) and unit sizes. This requires specific algebraic formulas for conversions: **Fahrenheit to Celsius**: $$C = (F - 32) \times \frac{5}{9}$$ **Celsius to Fahrenheit**: $$F = C \times \frac{9}{5} + 32$$ **Celsius to Kelvin**: $$K = C + 273.15$$ ## Why Metric Prefixes Make Sizing Easy The metric system is a decimalized system based on powers of 10. By adding standard prefixes (kilo for 1,000, centi for 1/100, milli for 1/1,000), you can scale units easily without memorizing arbitrary conversion factors like the 12 inches in a foot or 16 ounces in a pound. ## How to Use This Unit Converter Choose a category — Length, Weight, or Temperature — then select the source and target units and enter the value you want to convert. The converted result updates instantly as you type. Length and weight conversions route through a shared base unit (meters or grams) so any combination of units in that category converts accurately, while temperature uses its own direct formula since Celsius, Fahrenheit, and Kelvin do not share a common zero point. ## Worked Example: Length, Weight, and Temperature Converting 1 meter to feet returns 3.2808 feet, and converting 1 kilogram to pounds returns 2.2046 pounds — both computed by multiplying through the shared base-unit factor. Converting 32°F to Celsius returns exactly 0°C (freezing point of water), and converting 100°C to Fahrenheit returns exactly 212°F (boiling point of water at sea level) — confirmed by running the tool's actual conversion formulas against these reference points. ## Area and volume do not scale like length This is the single most expensive conversion mistake, and it catches experienced people. A length conversion factor applies to a length. For an area you must square it; for a volume you must cube it. One foot is 0.3048 m, so one **square** foot is 0.3048² = 0.0929 m², and one **cubic** foot is 0.3048³ = 0.0283 m³. Applying the linear 0.3048 to a volume understates it by roughly a factor of ten — enough to order a tenth of the concrete a slab needs. The same trap appears in scaling rather than converting. Doubling every dimension of a box multiplies its surface area by 4 and its volume by 8, which is why a model at 1:24 scale has 1/576 of the original's surface and 1/13,824 of its volume. Whenever a quantity is measured in units with a superscript, check that your factor carries the same superscript. ## Units that share a name but not a size Several everyday units are ambiguous, and a converter can only be as correct as the variant you pick. **Gallons.** A US liquid gallon is 3.785 L; an imperial gallon is 4.546 L — about 20% larger. Fuel-economy figures quoted in miles per gallon are not comparable across the two without conversion. **Fluid ounces.** A US fluid ounce is 29.57 mL, an imperial fluid ounce 28.41 mL. Confusingly, the imperial pint is 20 imperial fl oz and the US pint is 16 US fl oz, so an imperial pint is nearly 20% larger. **Tons.** A short ton is 2,000 lb (907 kg), a long ton 2,240 lb (1,016 kg), and a metric tonne 1,000 kg. **Miles**: the statute mile is 1,609 m, the nautical mile 1,852 m. **Calories**: a dietary Calorie is a kilocalorie, 1,000 of the calories used in physics. Where a figure matters, state the variant explicitly rather than relying on context — "3.5 US gal" rather than "3.5 gal". ## Mass, weight and rounding discipline Kilograms measure mass and newtons or pounds-force measure weight, which is mass times local gravity. On Earth the distinction rarely bites, because the pound is used for both mass and force and the ratio is effectively constant; off Earth, or in engineering work, it matters. A 70 kg person has 70 kg of mass everywhere and weighs about 686 N here and roughly 114 N on the Moon. For rounding, convert once at the end rather than at each step, and keep the precision of your least precise input. A measurement given as "6 feet" is precise to about half a foot, so reporting 1.8288 m implies four decimal places of accuracy that the original measurement never had — 1.8 m is the honest answer. Two conversions worth committing to memory as checks: 1 inch is exactly 2.54 cm by definition, and 1 kg is 2.2046 lb. If a converted figure is not roughly consistent with those, an input unit was selected wrongly. ## Related Calculators This converter is part of an Everyday Conversion Tools cluster. For construction material estimates, use the [Concrete Calculator](/calculators/concrete-calculator) or the [Square Footage Calculator](/calculators/square-footage-calculator). ## Frequently asked questions ### How is temperature conversion calculated? Fahrenheit to Celsius is calculated as (F - 32) x 5/9, while Celsius to Kelvin is calculated as C + 273.15. ### Why does the converter use a base unit? Using a single base unit per category reduces the number of conversion factors required, ensuring consistency and preventing precision loss. ### What is the metric system? An international decimalized system of measurement based on the meter, liter, and gram, using powers of 10 for scaling. ### What is the imperial system? A system of weights and measures originally used in Great Britain, defined by units like the inch, foot, yard, and pound. ### How many centimeters are in an inch? Exactly 2.54 centimeters are in one inch, which is the official international standard definition. ### How do I convert pounds to kilograms? Multiply the weight in pounds by 0.45359237, or divide by 2.20462 for a quick approximation. ### What is absolute zero? Absolute zero (0 Kelvin, or -273.15°C) is the lowest possible temperature where all molecular motion stops. ### Why does the US still use the imperial system? Historical usage, manufacturing standards, and the high cost of converting infrastructure have kept the US customary system in place. ### What is the difference between mass and weight? Mass is the amount of matter in an object (constant everywhere). Weight is the gravitational force acting on that mass (varies by gravity). ### How do I convert Celsius to Fahrenheit? Multiply the Celsius temperature by 1.8 (or 9/5) and add 32. ## Related concepts - **Metric system** — An international decimalized system of measurement based on the meter, liter, and gram. - **Imperial system** — A system of weights and measures originally used in Great Britain, defined by units like the inch, foot, and pound. - **Absolute Zero** — The zero point on the Kelvin scale, representing the complete absence of heat energy. ## Related guides - [Unit Conversion Guide: Length, Weight, Temperature](https://dothecalculation.com/blog/math/unit-conversion-methods) — Learn dimensional analysis and practical unit conversion for length, weight, and temperature with examples tied to the live DTC unit converter. - [Concrete Volume Guide: Slab Yardage, Waste Allowance, and Bag Estimates](https://dothecalculation.com/blog/utility/concrete-volume-estimation) — Learn how to calculate concrete volume for slabs and footings. 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Grade Point Averages depend on institution-specific grading scales. Unit conversions are based on standard conversion factors. Always verify critical metrics with official transcripts or engineering specifications._ --- _Source: [Do The Calculation](https://dothecalculation.com/calculators/unit-converter). Quote freely with attribution and a link to this page._