Science & engineering / QUICK REFERENCE
SI prefixes at a glance
The symbols and powers of ten that turn a unit into something much larger — or much smaller.
Larger than the base unit
- deca
- da · 10^1
Multiply the unprefixed unit by ten to the power 1. [1]
- hecto
- h · 10^2
Multiply the unprefixed unit by ten to the power 2. [1]
- kilo
- k · 10^3
Multiply the unprefixed unit by ten to the power 3. [1]
- mega
- M · 10^6
Multiply the unprefixed unit by ten to the power 6. [1]
- giga
- G · 10^9
Multiply the unprefixed unit by ten to the power 9. [1]
- tera
- T · 10^12
Multiply the unprefixed unit by ten to the power 12. [1]
- peta
- P · 10^15
Multiply the unprefixed unit by ten to the power 15. [1]
- exa
- E · 10^18
Multiply the unprefixed unit by ten to the power 18. [1]
- zetta
- Z · 10^21
Multiply the unprefixed unit by ten to the power 21. [1]
- yotta
- Y · 10^24
Multiply the unprefixed unit by ten to the power 24. [1]
- ronna
- R · 10^27
Multiply the unprefixed unit by ten to the power 27. [1]
- quetta
- Q · 10^30
Multiply the unprefixed unit by ten to the power 30. [1]
Smaller than the base unit
- deci
- d · 10^-1
Multiply the unprefixed unit by ten to the power -1. [1]
- centi
- c · 10^-2
Multiply the unprefixed unit by ten to the power -2. [1]
- milli
- m · 10^-3
Multiply the unprefixed unit by ten to the power -3. [1]
- micro
- µ · 10^-6
Multiply the unprefixed unit by ten to the power -6. [1]
- nano
- n · 10^-9
Multiply the unprefixed unit by ten to the power -9. [1]
- pico
- p · 10^-12
Multiply the unprefixed unit by ten to the power -12. [1]
- femto
- f · 10^-15
Multiply the unprefixed unit by ten to the power -15. [1]
- atto
- a · 10^-18
Multiply the unprefixed unit by ten to the power -18. [1]
- zepto
- z · 10^-21
Multiply the unprefixed unit by ten to the power -21. [1]
- yocto
- y · 10^-24
Multiply the unprefixed unit by ten to the power -24. [1]
- ronto
- r · 10^-27
Multiply the unprefixed unit by ten to the power -27. [1]
- quecto
- q · 10^-30
Multiply the unprefixed unit by ten to the power -30. [1]
PROVENANCE, NOT A PROMISE
Sources & verification
The prefix names, symbols and powers were checked against the BIPM table. Tests compare the stored entries to a fixed transcription of that table; they are regression checks, not an independent scientific review.
Independent review pending. This sheet was prepared with AI assistance. Source checks and automated tests do not establish universal correctness.
- SI prefixes ↗BIPM · accessed 2026-10-19
cheatsheetatlas.com/sheets/si-prefixes/ · Starter example · Revision 1 · 2026-10-19