The prefix yocto- is used to multiply the coefficient 10^-24 to the value of a physical quantity, so 1 yoctogram equals 1 * 10^-24 grams.

Warning: yocto- (yg) should not be confused with yotta- (Yg).

The coefficient is close to the reciprocal of Avogadro's number:

• 1 atomic mass unit = 1.660 54 yg

Although the amu is often convenient as a unit, one may sometimes want to use yoctograms to relate easily to other SI values.

It can be used for masses of nucleons, atoms and molecules. It is a little large for light particles, but yocto- is the last official prefix in the sequence. (For lengths such as the radius of an atom or even a proton the SI-prefixes are more than sufficient, but masses are proportional to the third power of the length, so one runs out of prefixes sooner; for volumes the extent of the range of prefixes is quite large, but the steps between them are very large too, e.g. 1nm³ = 1 000 000 000 pm³).

• Mass of electron: 0.000 91 yg
• Mass of proton : 1.672 6 yg
• Mass of neutron: 1.674 9 yg

Conversion of density: 1 kg/m³ = 1 yg/nm³.

See also

• Orders of magnitude (mass)
  • 1-10 yg
  • 10-100 yg