Femtometers to Centimeters (fm to cm)

1 femtometer equals 1×10⁻¹³ centimeters exactly.

1 femtometer = 1×10⁻¹³ centimeters

How to convert femtometers to centimeters

To convert femtometers to centimeters, multiply the number of femtometers by 1×10⁻¹³. This factor is exact. To go the other way, multiply centimeters by 10,000,000,000,000.

centimeters = femtometers × 1×10⁻¹³

Example: 10 femtometers = 1×10⁻¹² centimeters.

About these units

Femtometer (fm)

ScientificCurrent unit

One quadrillionth of a meter, also called a fermi. The scale of atomic nuclei; a proton is roughly 0.84 fm in radius.

Robert Hofstadter coined the nickname fermi for this length in a 1956 paper in Reviews of Modern Physics, honoring Enrico Fermi. The formal name comes from femto, which Wikipedia traces to the Danish and Norwegian word femten, meaning fifteen, a nod to the factor of 10 to the minus 15. The prefix entered the SI in 1964, and Hofstadter also used the term in his 1961 Nobel Lecture.

One femtometer is a quadrillionth of a meter, or 1,000 picometers. The unit suits atomic nuclei: Wikipedia gives a proton charge radius of about 0.841 fm and a gold nucleus radius of about 8.45 fm, so a heavy nucleus is roughly ten times wider than a proton. The 0.841 fm figure from that article is the one used here. Cross-sections in the same field are measured in barns, and one barn equals 100 square femtometers.

1 femtometer = 1×10⁻¹⁵ meters (exactly).

Sources: Wikipedia: Femtometre; Wikipedia: Metric prefix; NIST: metric (SI) prefixes

Centimeter (cm)

Metric (SI)Current unit

One hundredth of a meter. Used for body measurements, clothing and everyday objects.

Scientists, rather than shopkeepers, gave the centimeter its place. In 1832 Carl Friedrich Gauss proposed a system of absolute units built on length, mass and time, choosing the millimeter, milligram and second. In 1873 a committee of the British Association for the Advancement of Science, whose members included James Clerk Maxwell and William Thomson (Lord Kelvin), recommended the centimeter, gram and second instead. That CGS system dominated physics for decades, until the metre-kilogram-second system replaced it in the mid-twentieth century and led to SI.

CGS units proved awkward for rooms and buildings, which run to hundreds of centimeters, but the centimeter itself never went away. It is still the everyday unit for height, clothing and small objects, and it appears in map scales and rainfall reports. An adult fingernail is roughly one centimeter wide, and a milliliter is defined as exactly one cubic centimeter. An inch is exactly 2.54 centimeters. The CGS system itself survives mainly in theoretical physics and astrophysics, where Gaussian units are still common.

1 centimeter = 0.01 meters (exactly).

Sources: Wikipedia: Centimetre-gram-second system of units; Wikipedia: Centimetre; NIST Guide to the SI, Appendix B.8: conversion factors

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