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The yoctometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: ym) or yoctometer (American spelling) is an SI measure of length that is equal to 1024 (yocto) of a metre. A yoctometre is equivalent to 1/100,000 the diameter of a proton or neutron.[citation needed]

  • 1 ym = 1×1024 metre

In terms of relative length of units, a yoctometre ranks as follows: Planck length << yoctometre << zeptometre. A yoctometre is 1/1000 of a zeptometre (1 zeptometre (zm) = 1,000 yoctometres). The yoctometre,is the distance light travels in about:1÷2.99×1035 seconds.

Measurement Equivalents[edit]

There are some objects in the universe that can easily define yoctometre.They are considered as the smallest objects in the universe.


They are smaller than any particle,composes atoms.They are commonly about a yoctometer and some are zeptometres.


Because the yoctometre is much smaller than the radius of an atom, it is useful only for measuring very small subatomic particles such as quarks. Larger subatomic particles such as protons and other hadrons are usually measured in femtometers (10-15 m, or 109 ym.

See also[edit]