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# Orders of magnitude

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Orders of magnitude
Length - Mass - Time - Area - Volume - Power - Temperature - Numbers - Data - U.S. money
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SI base units - SI derived units - SI prefixes
An order of magnitude is a factor of ten. For example, two numbers are said to differ by "three orders of magnitude" if they differ by three factors of ten, that is one is approximately 1000 times larger than other.

The order of magnitude of a number is, intuitively speaking, the number of powers of 10 contained in the number or a close approximation to it. More precisely, the order of magnitude of a number can be defined in terms of the logarithm of the number to the base of 10, usually as the integer part of the logarithm. Thus the order of magnitude of 400 is 2. The order of magnitude of a number may also be defined as the exponent of the power of 10 when the number is represented using scientific notation.

An order of magnitude estimate of a variable whose precise value is unknown is an estimate rounded in some way to the nearest power of 10. For example, an accurate order of magnitude estimate for the human population of the Earth in the year 2000 is 10 billion. An order of magnitude estimate is sometimes also 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, energy or temperature. 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.

## Orders of magnitude of various quantities

In the following table the different quantities are lined up so that the following are in the same row:

See also the separate tables for time, length, area, volume, mass, energy, power, temperature and dimensionless numbers.

Time Length Area Volume Mass Energy Temperature
(x 3)* (m) (m2) (m3) (kg) (J) (K)
(second) (metre) (square metre) (cubic metre) (kilogram) (joule) (kelvin)**
10-44 s 10-35 m
...
10-28 s 100 zm
10-27 s 1 am
1 E-9 K>1 nK
10-26 s 10 am       1 peV

1 E-6 K>1 µK
10-25 s 100 am
1 E-3 K>1 mK
10-24 s 1 fm       0.001 meV
0.01 meV
0.1 meV

1 E0 K>1 K
10-23 s 10 fm       1 meV
10 meV
100 meV
10 K
100 K
1000 K
10-22 s 100 fm 10-28 m2     1 eV
10 eV
100 eV
10,000 K
100,000 K
106 K
10-21 s 1 pm     10-33 kg
10-32 kg
10-31 kg
1000 eV
104 eV
105 eV

1 E9 K>109 K
10-20 s 10pm     10-30 kg
10-29 kg
10-28 kg
1 MeV
10 MeV
100 MeV

1 E9 K>109 K
10-20 s 10pm     10-30 kg
10-29 kg
10-28 kg
1 MeV
10 MeV
100 MeV

1 E12 K>1012 K
10-19 s 100 pm 10-20 m2
10-19 m2
10-27 kg
10-26 kg
10-25 kg
1 GeV
10 GeV
100 GeV

1 E15 K>1015 K
10-18 s 1 nm 10-18 m2
10-17 m2
10-24 kg
10-23 kg
10-22 kg
1 TeV
10 TeV
100 TeV

1 E18 K>1018 K
10-17 s 10 nm 10-16 m2
10-15 m2
10-21 kg
10-20 kg
10-19 kg
0.0001 J
0.001 J
0.01 J

1 E21 K>1021 K
10-16 s 100 nm 10-14 m2
10-13 m2
10-21 m3
10-20 m3
10-19 m3
10-18 kg
10-17 kg
10-16 kg
0.1 J
1 J
10 J

1 E24 K>1024 K
1 fs 1 μm 10-12 m2
10-11 m2
10-18 m3
10-17 m3
10-16 m3
10-15 kg
10-14 kg
10-13 kg
100 J
1000 J
10000 J

1 E27 K>1027 K
10 fs 10 μm 10-10 m2
10-9 m2
10-15 m3
10-14 m3
10-13 m3
10-12 kg
10-11 kg
10-10 kg
100000 J
0.001 kWh
0.01 kWh

1 E30 K>1030 K
100 fs 100 μm 10-8 m2
10-7 m2
10-12 m3
10-11 m3
10-10 m3
10-9 kg
10-8 kg
10-7 kg
0.1 kWh
1 kWh
10 kWh

1 ps 1 mm 10-6 m2
10-5 m2
10-9 m3
10-8 m3
10-7 m3
10-6 kg
10-5 kg
10-4 kg
100 kWh
1000 kWh
10000 kWh

10 ps 1 cm 1 cm2
10 cm2
1 ml
10 ml
100 ml
1 g
10 g
100 g
100000 kWh
1 GWh
10 GWh

100 ps 10 cm 0.01 m2
0.1 m2
1 l
10 l
100 l
1 kg
10 kg
100 kg
100 GWh
1000 GWh
10000 GWh

1 ns 1 m 1 m2
10 m2
1 m3
10 m3
100 m3
1 t
10 t
100 t
100000 GWh
106 GWh
107 GWh

10 ns 10 m 100 m2
1,000 m2
1,000 m3
10,000 m3
105 m3
106 kg
107 kg
108 kg
108 GWh
109 GWh

100 ns 100 m 1 ha
10 ha
106 m3
107 m3
108 m3
109 kg
1010 kg
1011 kg
1 E27 J>1012 GWh

1 μs 1 km 1 km2
10 km2
1 km3
10 km3
100 km3
1012 kg
1013 kg
1014 kg
1 E30 J>1015 GWh

10 μs 10 km 108 m2
109 m2
1012 m3

1015 kg
1016 kg
1017 kg
1 E33 J>1018 GWh

100 μs 100 km 1010 m2
1011 m2
1015 m3

1018 kg
1019 kg
1020 kg
1 E36 J>1021 GWh

1 ms 1000 km 1012 m2
1013 m2
1018 m3

1021 kg
1022 kg
1023 kg
1 E39 J>1024 GWh

10 ms 104 km 1014 m2
1015 m2
1021 m3

1024 kg

1 E42 J>1027 GWh

100 ms 105 km 1016 m2
1017 m2
1024 m3

1027 kg

1 E45 J>1030 GWh

1 s 106 km 1018 m2
1019 m2
1027 m3

1030 kg

1 E48 J>1033 GWh

10 s 107 km 1020 m2
1021 m2
1033 kg

1 E51 J>1036 GWh

100 s 1 AU     1036 kg

1 E54 J>1039 GWh

1 h 10 AU     1039 kg

1 E57 J>1042 GWh

10 h 100 AU     1042 kg

1 E60 J>1045 GWh

1 day 1000 AU     1045 kg

1 E63 J>1048 GWh

10 day 104 AU     1048 kg

1 E66 J>1051 GWh

1 yr 1 LY     1051 kg

1 E69 J>1054 GWh

10 yr 10 LY
100 yr 100 LY
1000 yr 1000 LY
104 yr 104 LY 1040 m2
1041 m2

105 yr 105 LY
106 yr 106 LY
107 yr 107 LY
108 yr 108 LY
109 yr 109 LY
1010 yr 1010 LY
1011 yr
1012 yr
and more

* Each time shown is linked to that time. However, the time taken for light to cross the corresponding length is 3 times the time shown.

** These are the standard units but this table uses a variety of units, which can make it harder to read.

## Units used in the table

The table uses units and prefixes that are commonly recognized: