WiseCalcs

Unit converter

Pick a category, choose the units to convert from and to, and enter a value. The converted result updates as you type.

Use it to convert a value between two units in the same category — length, mass, or temperature.

Category

Converted value

1 km

1,000 m = 1 km

The result updates as you type. Use the swap button to reverse the from and to units.

How does it work?

Length and mass convert through a base unit using exact factors. Temperature uses explicit formulas, not a single factor.

Unit conversion

length / mass:vto=vfrom⋅ffromftotemperature:°F=°C⋅95+32,K=°C+273.15\begin{aligned} &\textbf{length / mass:}\quad v_{to} = v_{from}\cdot\dfrac{f_{from}}{f_{to}}\\[4pt] &\textbf{temperature:}\quad °F = °C\cdot\tfrac{9}{5}+32,\quad K = °C+273.15 \end{aligned}
v_{from}
The value in the source unit.
f_{from}, f_{to}
Each unit's factor to the base unit (metre or kilogram).
°C, °F, K
Temperature in Celsius, Fahrenheit, or Kelvin.

1 mi = 1609.344 m. 100 °C = 212 °F = 373.15 K. 1 lb = 0.45359237 kg.

Method & sources

Length and mass convert through a base unit (metre, kilogram) using exact internationally defined factors, for example 1 in = 0.0254 m and 1 lb = 0.45359237 kg. Temperature uses explicit Celsius, Fahrenheit, and Kelvin formulas, not a single scaling factor. Units only convert within the same category; you cannot convert a length to a mass.

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

How we calculate

  • Length and mass convert through a base unit (metre, kilogram) using exact internationally defined factors, for example 1 in = 0.0254 m and 1 lb = 0.45359237 kg.
  • Temperature uses explicit Celsius, Fahrenheit, and Kelvin formulas, not a single scaling factor.
  • Units only convert within the same category; you cannot convert a length to a mass.

Rounding

The converted value is shown with up to six decimal places for readability. The calculation itself uses full precision.

What this calculator does

This converter changes a value from one unit to another within a chosen category. It supports length (m, km, cm, mm, mi, yd, ft, in), mass (kg, g, mg, lb, oz), and temperature (Celsius, Fahrenheit, Kelvin).

How to use it

  1. Choose a category: length, mass, or temperature.
  2. Select the unit to convert from and the unit to convert to.
  3. Enter the value, and read the converted result below.

How the conversion works

Length and mass convert through a base unit using exact factors: each unit is first turned into the base (metre or kilogram), then into the target unit. Temperature is different — Celsius, Fahrenheit, and Kelvin are related by explicit formulas, not a single multiplier, so the converter applies those directly.

A worked example

Convert 1000 metres to kilometres and you get 1 km. Convert 1 mile and you get 1609.344 metres. In temperature, 100 °C equals 212 °F and 373.15 K, while 0 °C equals 32 °F and 273.15 K.

Common mistakes

  • Trying to convert across categories, such as a length to a mass — units only convert within the same category.
  • Treating temperature like a simple factor. 100 °F is not double 50 °F because Fahrenheit does not start at zero.
  • Mixing up similar symbols, for example mi (mile) with mm (millimetre).

When it's useful

Recipes, travel, DIY measurements, science homework, and any time a value is given in one unit but you need another.

FAQ

Which units can I convert?
Length (m, km, cm, mm, mi, yd, ft, in), mass (kg, g, mg, lb, oz), and temperature (Celsius, Fahrenheit, Kelvin).
How accurate are the conversions?
Length and mass use exact internationally defined factors, such as 1 inch = 0.0254 m and 1 pound = 0.45359237 kg. The displayed value is rounded for readability, but the calculation uses full precision.
Why isn't temperature just a multiplication?
Temperature scales do not share a zero point, so converting needs an offset as well as a scale. The converter uses the standard Celsius, Fahrenheit, and Kelvin formulas.
Can I convert a length into a mass?
No. Units only convert within the same category. Changing the category resets the from and to units to that category.
What does the swap button do?
It reverses the from and to units so you can convert in the opposite direction without re-selecting them.
Can I share a conversion?
Yes. Use Share to copy a link that reopens the converter with the same category, units, and value.

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