Miles to Femtometers (mi to fm)

1 mile equals 1.609344×10¹⁸ femtometers exactly.

1 mile = 1.609344×10¹⁸ femtometers

How to convert miles to femtometers

To convert miles to femtometers, multiply the number of miles by 1.609344×10¹⁸. This factor is exact. To go the other way, multiply femtometers by 6.213711922×10⁻¹⁹ (rounded).

femtometers = miles × 1.609344×10¹⁸

Example: 10 miles = 1.609344×10¹⁹ femtometers.

About these units

Mile (mi)

US & ImperialCurrent unit

5,280 feet or 1,760 yards, exactly 1,609.344 meters. This is the statute (international) mile used on US and UK roads.

A thousand paces gave the mile its name. It descends from the Latin mille passus, the Roman mile, by way of Old English mil and Middle English myle. For centuries after Rome, miles of many lengths coexisted; a sixteenth-century Mercator map, for example, shows small, medium and large Flemish miles on a single scale bar. The English statute mile was fixed by an Act of Parliament under Elizabeth I in 1593, which declared that a mile contains eight furlongs, or 5,280 feet.

The 1959 international yard and pound agreement made that mile exactly 1,609.344 meters. A slightly longer US survey mile, about 1,609.347 meters, lingered in American land surveys and was slated for retirement from 1 January 2023. Today the mile is the road unit of the United Kingdom, the United States, Liberia and Myanmar, along with several territories such as the Bahamas, Belize, Guam and the US Virgin Islands. In Canada it survives chiefly in rail transport and horse racing.

1 mile = 1,609.344 meters (exactly).

Sources: Wikipedia: Mile; Wikipedia: Foot (unit); NIST Guide to the SI, Appendix B.8: conversion factors

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

Related conversions

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