Conversion Calculator

Convert between temperature, length, area, volume, and weight units instantly.

Supports metric, imperial, and specialized units with instant bidirectional conversion.

Updated August 19, 2026

CreatorFrank Zhao

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Introduction / overview

This conversion calculator bundles five separate converters into one page. Pick a category — temperature, length, area, volume, or weight — and every field in that category updates together as you type. Type a value into any unit and the others recalculate instantly, so you can convert in either direction without switching tools.

Supported conversion types

Temperature

°C, °F, K, °R, °De

Length

mm → km, in → mi, nmi

Area

mm² → km², in² → mi²

Volume

mL → L, in³ → gal

Weight

µg → t, oz → ton

Bidirectional conversion

Type into any field and every other field updates instantly. No “from” / “to” direction needed — just enter a value and read the rest.

Metric ↔ Imperial ↔ Custom units

Grouped by system

Units are organized into Metric, Imperial/US, and Other sections — find what you need without scrolling through an alphabetical list.

Smart grouping with unit dropdowns

Already know what you need?

If you work with one measurement type all the time, a dedicated tool can be more convenient — try the length converter, weight converter, or temperature converter.

How to use / quick start

Choose the conversion type

Select Temperature, Length, Area, Volume, or Weight from the dropdown at the top.

Pick the right unit

If the unit you want is not the default, open the dropdown on the right of any field and select it.

Type a value

Enter a number into any field. Every other field in that category recalculates instantly.

Read the results

You can edit any field and the rest follow — so converting back is just as easy as converting forward.

Try it: convert a baking temperature

A recipe calls for $200\,^\circ\mathrm{C}$ and you want the Fahrenheit value. Choose Temperature, type $200$ into the Celsius field, and read the Fahrenheit field:

T_{^\circ\mathrm{F}}

=

\tfrac{9}{5}\,T_{^\circ\mathrm{C}} + 32

=

\tfrac{9}{5}(200) + 32

=

392\,^\circ\mathrm{F}

Because the conversion runs in both directions, you can also type a Fahrenheit value and read Celsius.

Calculation method

For length, area, volume, and weight, every unit is converted through a single base unit — the meter, the square meter, the cubic meter, and the kilogram. A value in any unit is first expressed in the base unit, then converted to the unit you are reading:

\text{value}_{\text{target}} = \text{value}_{\text{source}} \times \frac{f_{\text{source}}}{f_{\text{target}}}

where $f$ is each unit's factor relative to the base unit. For example, since $1\ \mathrm{m} = 100\ \mathrm{cm}$ and $1\ \mathrm{m} \approx 3.28084\ \mathrm{ft}$ , converting $2\ \mathrm{m}$ to feet:

2 \times 3.28084

\approx

6.56168\ \mathrm{ft}

Area and volume scale by the square and the cube

A common mistake is treating area and volume prefixes like length prefixes. Because area is length squared and volume is length cubed, the factor is squared or cubed too:

1\ \mathrm{km}^2

=

(1000\ \mathrm{m})^2

=

1{,}000{,}000\ \mathrm{m}^2

A square kilometer is one million square meters, not one thousand. The same applies to cubic units: $1\ \mathrm{m}^3 = 1{,}000{,}000\ \mathrm{cm}^3$ .

Temperature uses offsets, not just ratios

Temperature scales are the exception: they are related by a linear formula with an offset, because the zero point differs between scales. The converter applies these standard relationships:

T_{^\circ\mathrm{F}} = \tfrac{9}{5}\,T_{^\circ\mathrm{C}} + 32

T_{\mathrm{K}} = T_{^\circ\mathrm{C}} + 273.15

Rankine uses an absolute scale like Kelvin but in Fahrenheit-sized degrees, while Delisle, Newton, Réaumur, and Rømer are historical scales with their own offsets and factors. You can select them from the dropdown on the two “Other temperature units” fields.

US and UK units are not the same

Several volume and weight units share names but differ in size between the US customary and UK imperial systems. A US gallon is about $3.785\ \mathrm{L}$ , while a UK gallon is about $4.546\ \mathrm{L}$ . The same is true for fluid ounces, pints, and quarts. The converter keeps these as separate options, so check which one your source uses before converting.

Real-world examples

Furniture that fits a doorway

A desk is listed as $180\ \mathrm{cm}$ wide, but you want to check it against a doorway measured in inches. Choose Length, type $180$ into a metric field:

180\ \mathrm{cm} = 1.8\ \mathrm{m} \approx 70.87\ \mathrm{in}

If the doorway is $72\ \mathrm{in}$ , the desk will not fit — a quick check that saves a delivery headache.

Reading a package weight

A parcel weighs $2.5\ \mathrm{kg}$ , but the shipping form asks for pounds. Choose Weight, type $2.5$ into a metric field:

2.5\ \mathrm{kg} \approx 5.51\ \mathrm{lb}

The converter also shows the value in ounces, tons, and the other weight units, so you can pick the one the form expects.

Comparing a recipe volume

A US recipe calls for $1\ \mathrm{cup}$ of milk, but your measuring jug is in milliliters. Choose Volume, type $1$ into the cups field:

1\ \mathrm{US\ cup} \approx 236.59\ \mathrm{mL}

Because the converter separates US and UK units, you can also check the UK fluid-ounce equivalent if your recipe uses imperial measures.

Limitations / disclaimers

This is a general unit converter, not a source of authoritative measurement standards. A few points to keep in mind:

US and UK units with the same name differ in size — always confirm which system your value uses.
Some units are conventions rather than exact definitions. For example, a soccer field is treated as 7,140 m², and kitchen tablespoons as 15 mL; real values can vary.
Astronomical and particle units (light years, parsecs, atomic mass units) use widely accepted approximations, which are fine for everyday comparison but not for precision science.
Results are rounded for display. For exact work, use the full-precision value shown by the calculator.

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