Why does my phone give a slightly different answer?

Quick converters often use pre-rounded factors, such as treating an inch as 2.54 cm to two decimals, and the error compounds across conversions. This engine uses the defined values and rational forms — a 台尺 is 10/33 m, not 0.303 m — so converting there and back returns the original number.

Which categories are supported?

Length, mass, temperature, area, volume, speed, data size, data rate, power, energy, pressure, angle, and time — thirteen in all. The Taiwanese 坪, 台斤, and 台尺 are included with their exact definitions.

UNIT CONVERSION · CALCULATED FROM DEFINITIONS

Unit Converter

Convert length, mass, temperature, area, data, and more across 13 categories.

From

Formulain = cm × 0.393700787

Ratio1 cm = 0.393700787 in

Every unit in this category

m0.01Metre

km0.00001Kilometre

mm10Millimetre

µm10,000Micrometre

in0.393700787Inch

ft0.032808399Foot

yd0.010936133Yard

mi0.000006214Mile

nmi0.0000054Nautical mile

台尺0.033Taiwanese foot

Common values

cm	in
`0.5 cm`	`0.196850394 in`
`1 cm`	`0.393700787 in`
`2 cm`	`0.787401575 in`
`3 cm`	`1.181102 in`
`5 cm`	`1.968504 in`
`10 cm`	`3.937008 in`
`15 cm`	`5.905512 in`
`20 cm`	`7.874016 in`
`25 cm`	`9.84252 in`
`30 cm`	`11.811024 in`
`50 cm`	`19.685039 in`
`75 cm`	`29.527559 in`
`100 cm`	`39.370079 in`
`150 cm`	`59.055118 in`
`200 cm`	`78.740157 in`
`500 cm`	`196.8504 in`
`1000 cm`	`393.7008 in`

About this tool

Pick a category, choose the source and target units, and enter a value to get the result, the formula behind it, and that value expressed in every other unit in the category. Factors are the definitions themselves — an inch is exactly 0.0254 m, a 坪 is exactly 400/121 m², a Fahrenheit degree is exactly 5/9 of a kelvin — so repeated conversions do not accumulate rounding error.

How it works

Choose a category such as length or data size.
Choose the source and target units, and swap if needed.
Enter a value to see the result, the formula, and every other unit.

Precision and definitions

Uses defined conversion factors rather than pre-rounded approximations. Everything is calculated in your browser.

Privacy

Every conversion runs inside this browser. The values you enter are never uploaded, stored, or written to the URL or any log.

Frequently asked questions

Why does my phone give a slightly different answer?: Quick converters often use pre-rounded factors, such as treating an inch as 2.54 cm to two decimals, and the error compounds across conversions. This engine uses the defined values and rational forms — a 台尺 is 10/33 m, not 0.303 m — so converting there and back returns the original number.
Which categories are supported?: Length, mass, temperature, area, volume, speed, data size, data rate, power, energy, pressure, angle, and time — thirteen in all. The Taiwanese 坪, 台斤, and 台尺 are included with their exact definitions.

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