Scientific Notation

Astronomy deals with big numbers. Really big numbers. It’s impossible to talk about the distance to the Sun or the speed of light without thinking about the tremendously huge. But big numbers intrude on all aspects of our lives and as responsible citizens, we ought to have a way of dealing with them. You need only drive past a McDonald’s restaurant to see that numbers larger than a billion (or however many they’ve served by now) are commonplace in our society. On a more serious note, a person must have an understanding of the word "trillions" in order to comprehend the size of the National Debt.

Mathematicians and scientists use scientific notation to handle large numbers. Scientific notation is necessary when discussing astronomical quantities, unless we want to write out a lot of zeros ("Excuse me, Dr. Sagan, did you say the Universe began 15,000,000,000 years ago or 150,000,000,000 years ago?"). Scientific notation is also essential for dealing with extremely small numbers, such as the mass of a Hydrogen atom or the wavelength of visible light.

The following table and tips are intended to be used as a reference:


Decimal Representation

Scientific Notation

Metric Prefix


one billionth 0.000000001 1 x 10-9


one hundred-millionth 0.00000001 1 x 10-8    
one ten-millionth 0.0000001 1 x 10-7    
one millionth 0.000001 1 x 10-6


one hundred-thousandth 0.00001 1 x 10-5    
one ten-thousandth 0.0001 1 x 10-4    
one thousandth 0.001 1 x 10-3 milli m
one hundredth 0.01 1 x 10-2 centi c
one tenth 0.1 1 x 10-1 deci d
one 1 1 x 100    
ten 10 1 x 101    
one hundred 100 1 x 102    
one thousand 1,000 1 x 103 kilo k
ten thousand 10,000 1 x 104    
one hundred thousand 100,000 1 x 105    
one million 1,000,000 1 x 106 Mega M
ten million 10,000,000 1 x 107    
one hundred million 100,000,000 1 x 108    
one billion 1,000,000,000 1 x 109 Giga G
ten billion 10,000,000,000 1 x 1010    
one hundred billion 100,000,000,000 1 x 1011  
one trillion 1,000,000,000,000 1 x 1012 Tera T