Resource: Prefixes

All prefixes in the SI-system:[1,2]

Yotta...1\,\mathrm Y\ldots=10^{24}\ldots24 zeros (septillion)
Zetta...1\,\mathrm Z\ldots=10^{21}\ldots21 zeros (sextillion)
Exa...1\,\mathrm E\ldots=10^{18}\ldots18 zeros (quintillion)
Peta...1\,\mathrm P\ldots=10^{15}\ldots15 zeros (quadrillion)
Tera...1\,\mathrm T\ldots=10^{12}\ldots12 zeros (trillion)
Giga...1\,\mathrm G\ldots=10^{9}\ldots9 zeros (billion)
Mega...1\,\mathrm M\ldots=10^{6}\ldots6 zeros (million)
Kilo...1\,\mathrm k\ldots=10^{3}\ldots3 zeros (thousand)
Hecto...1\,\mathrm h\ldots=10^{2}\ldots2 zeros (hundred)
Deka...1\,\mathrm {da}\ldots=10^{1}\ldots1 zero (ten)
Deci...1\,\mathrm {d}\ldots=10^{-1}\ldots1 place after the point
Centi...1\,\mathrm {c}\ldots=10^{-2}\ldots2 places after the point
Milli...1\,\mathrm {m}\ldots=10^{-3}\ldots3 places after the point
Micro...1\,\mathrm {\mu}\ldots=10^{-6}\ldots6 places after the point
Nano...1\,\mathrm {n}\ldots=10^{-9}\ldots9 places after the point
Pico...1\,\mathrm {p}\ldots=10^{-12}\ldots12 places after the point
Femto...1\,\mathrm {f}\ldots=10^{-15}\ldots15 places after the point
Atto...1\,\mathrm {a}\ldots=10^{-18}\ldots18 places after the point
Zepto...1\,\mathrm {z}\ldots=10^{-21}\ldots21 places after the point
Yocto...1\,\mathrm {y}\ldots=10^{-24}\ldots24 places after the point

Examples of magnitude scale for the prefixes (shown for size with the metre unit):1

Size scale
Yottametres\mathrm{Ym}The universe5
Petametres\mathrm{Pm}Distance to nearest stars3
Terametres\mathrm{Tm}The solar system2
Gigametres\mathrm{Gm}The Sun[12]
Megametres\mathrm{Mm}The Earth[11]
Micrometres\mathrm{\mu m}Bacteria[9]
Zeptometres\mathrm{zm}Smallest quark[4]
Yoctometres\mathrm{ym}Smallest particle[4,3]

A feeling of the size scale is shown in the Youtube video Power of Ten (1977) and can be interactively scrolled in in [4].


  1. The International System of Units (SI)’ (book), B. Inglis, J. Ullrich and others, Bureau International des Poids et Mesures (BIPM), 9th ed., 2019,, chapter 3
  2. Guide for the Use of the International System of Units (SI)’ (article), Ambler Thompson & Barry N. Taylor, National Institute of Standards and Technology, 2008,
  3. Biotechnology’ (book), P. David Clark & Nanette J. Pazdernik, Newnes, 2nd ed., 2015,, ISBN 9780123850164
  4. The Scale of the Universe 2’ (web page), Cary Huang & Michael Huang,, 2012, (accessed May 3rd, 2019)
  5. Limits on the effective quark radius from inclusive ep scattering at HERA’ (article), H. Abramowicz, I. Abt and others, Physics Letters B, vol. 757, 2016,, DOI 10.1016/j.physletb.2016.04.007
  6. Electronics (+ and -) Protons, Photons, Neutrons, and Cosmic Rays’ (book), Robert Andrews Millikan, Cambridge University Press, 1st ed., 1935,
  7. The size of the proton’ (web page), Christine Nattrass, Quantum Diaries, (accessed May 3rd, 2019)
  8. Screening of membrane surface charges by divalent cations: an atomic representation’ (article), J. S. D’Arrigo, American Journal of Physiology: Cell Physiology, vol. 235, issue 3, 1978,, DOI 10.1152/ajpcell.1978.235.3.C109, pages 109–117
  9. Small but Mighty: Cell Size and Bacteria’ (article), Petra Anne Levin (Department of Biology at Washington University) & Esther R. Angert (Department of Microbiology at Cornell University), Cold Spring Harbor Laboratory Press Biol, 2015,, pages 2-3
  10. Highest Mountain in the World’ (web page),, (accessed May 3rd, 2019)
  11. How Big Is Earth?’ (web page), Tim Sharp,, 2017, (accessed May 3rd, 2019)
  12. The Sun’ (web page), NASA, (accessed May 3rd, 2019)
  13. Our Solar System, In Depth, Size and Distance’ (web page), NASA, 2019, (accessed May 3rd, 2019)
  14. PIA17046: Voyager Goes Interstellar’ (web page), JPL-Caltech, NASA, Jet Propulsion Laboratory at California Institute of Technology, 2013, (accessed May 3rd, 2019)
  15. The Nearest Stars to Earth (Infographic)’ (web page), Karl Tate,, 2012, (accessed May 3rd, 2019)
  16. 30 Doradus (NGC 2070) (Tarantula Nebula)’ (web page), Robert Gendler, Astrophotography by Robert Gendler, 2016, (accessed May 3rd, 2019)
  17. Our Milky Way Galaxy: How Big is Space?’ (web page), Pat Brennan, NASA Exoplanet Exploration, 2019, (accessed May 3rd, 2019)
  18. Sizes of Galaxies’ (web page),, (accessed May 3rd, 2019)
  19. Misconceptions about the Big Bang’ (article), Charles H. Lineweaver & Ramara M. Davis, Scientific American, 2005,, pages 36–45

Related Articles