The **femtometer****(fm**) is a unit of length in the International System of Units (SI). It corresponds to **10⁻¹⁵ meters** and is often used in nuclear physics, for example to describe the radius of atomic nuclei.

## Calculator

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**Use calculator:**

- Enter the number of femtometers in the calculator.
- Select the unit into which the femtometers are to be converted.
- Click on

The conversion between femtometers and other units of length is essential in order to understand and describe physical phenomena in different orders of magnitude.

## Conversion to SI base units

**Femtometer in meters (m):**$1fm=1_{^-15}m$

The conversion from femtometers to the base unit meter is given directly by the definition factor.

## Conversion to other SI-derived units

**Femtometer in millimeters (mm):**$1fm=1_{^-}_{18}mm$**Femtometer in micrometers (µm):**$1fm=1_{^-}_{21}µm$**Femtometer in nanometers (nm):**$1fm=1_{^-}_{12}nm$**Femtometer in picometer (pm):**$1fm=1_{^-}_{3}pm$

## Conversion to imperial and US units

The metric system is the most widely used internationally, but imperial units are still used in some regions, particularly in the USA.

**Femtometer in inches (in):**Since 1 inch is defined as 0.0254 meters:**$1fm=3,937×1_{^-}_{14}in$****Femtometer in feet (ft):**Using 12 inches per foot results in:**$1fm=3,2808×1_{^-}_{16}ft$**

## Practical application

The use of the femtometer is mainly limited to areas such as nuclear physics. For example, a proton in an atomic nucleus has an approximate radius of 0.84-0.87 fm. It is important to note that on such tiny scales, classical physics is not sufficient to describe phenomena and quantum mechanical models are needed.

## Conclusion

The femtometer is an extremely small unit of length that helps us to describe the tiny dimensions of atomic nuclei and other subatomic particles. Although it is rarely used in everyday life, it is crucial in scientific research to unravel the mysteries of the universe at the smallest scale. Understanding how to convert fm to other units allows scientists to interpret data in a more understandable context.