An order of magnitude is a factor of ten. For example, two numbers are said to differ by "3 orders of magnitude" if one is 1000 times larger than other. Orders of magnitude are quite easily and commonly described through the use of scientific notation and powers of ten. An order of magnitude estimate is not concerned with the precise value, but instead with the number of decimal digits after the first. It can also be called a zeroth order approximation.
One way of categorising things in the physical world is by their size. The pages below contain lists of items that are of the same order of magnitude in time, length, area, volume, mass, or energy. This is useful for getting an intuitive sense of the comparative size of things and the overall scale of the universe. SI units are used together with SI prefixes: these were devised with orders of magnitude in mind. Each individual page also gives other units; see also conversion of units.
In the following table the different quantities are lined up so that the following are in the same row: length and the time taken by light to cross that length, area of a square and the length of one side, volume of a cube and the area of one face, mass of some water and its volume. See also the separate tables for length, area, volume, mass, time and dimensionless numbers.
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2 See also
3 External links
Units used in the table
The table uses units and prefixes that are commonly recognized: