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Overview

SI Unit Prefixes

SI prefixes are prefixes used in the International System of Units (SI) to indicate multiples of units. They correspond to powers of 10 and range from large values (kilo, mega, giga, tera, etc.) to small values (milli, micro, nano, etc.). In 2022, four new prefixes (ronna, quetta, ronto, quecto) were added for the first time in 31 years, bringing the total to 24 prefixes currently in use. This system is essential for concisely expressing large and small numbers in science, technology, and everyday life.

International System of Units SI units unit conversion prefixes science technology
code slug name description category decimalValue powerOfTen
Q quetta quetta SI prefix representing 10 to the power of 30. large 1000000000000000000000000000000 30
R ronna ronna SI prefix representing 10 to the power of 27. large 1000000000000000000000000000 27
Y yotta yotta SI prefix representing 10 to the power of 24. large 1000000000000000000000000 24
Z zetta zetta SI prefix representing 10 to the power of 21. large 1000000000000000000000 21
E exa exa SI prefix representing 10 to the power of 18. large 1000000000000000000 18
P peta peta SI prefix representing 10 to the power of 15. large 1000000000000000 15
T tera tera SI prefix representing 10 to the power of 12. large 1000000000000 12
G giga giga SI prefix representing 10 to the power of 9. large 1000000000 9
M mega mega SI prefix representing 10 to the power of 6. large 1000000 6
k kilo kilo SI prefix representing 10 to the power of 3 (1000). large 1000 3
h hecto hecto SI prefix representing 10 to the power of 2 (100). large 100 2
da deca deca SI prefix representing 10 to the power of 1 (10). large 10 1
d deci deci SI prefix representing 10 to the power of -1 (0.1). small 0.1 -1
c centi centi SI prefix representing 10 to the power of -2 (0.01). small 0.01 -2
m milli milli SI prefix representing 10 to the power of -3 (0.001). small 0.001 -3
μ micro micro SI prefix representing 10 to the power of -6 (0.000001). small 0.000001 -6
n nano nano SI prefix representing 10 to the power of -9 (0.000000001). small 0.000000001 -9
p pico pico SI prefix representing 10 to the power of -12. small 0.000000000001 -12
f femto femto SI prefix representing 10 to the power of -15. small 0.000000000000001 -15
a atto atto SI prefix representing 10 to the power of -18. small 0.000000000000000001 -18
z zepto zepto SI prefix representing 10 to the power of -21. small 0.000000000000000000001 -21
y yocto yocto SI prefix representing 10 to the power of -24. small 0.000000000000000000000001 -24
r ronto ronto SI prefix representing 10 to the power of -27. small 0.000000000000000000000000001 -27
q quecto quecto SI prefix representing 10 to the power of -30. small 0.000000000000000000000000000001 -30

Prefixes defined by the International System of Units (SI) to represent multiples of units.