Units of Length
The fundemental unit for measuring length is the meter.
There are also other units for measuring large and small quantities, the most common are:
| kilometer | km | 1,000 m |
| hectometer | hm | 100 m |
| decameter | dam | 10 m |
| meter | m | 1 m |
| decimeter | dm | 0.1 m |
| centimeter | cm | 0.01 m |
| millimeter | mm | 0.001 m |
Note that each unit is 10 times larger than the previous.
Therefore, the problem of converting units to other units becomes an issue of multiplying or dividing the unit by one followed by as many zeros as there are places between them on the table above.
50 m 
cm
In this case, multiply (because the m is greater than the cm) the unit by one followed by two zeros, since there are two places between both units.
50 · 100 = 5,000 cm
4,385 mm m
In this case, divide (because the mm is smaller than the m) by one followed by three zeros, since there are three places between both units.
4385 : 1,000 = 4.385 m
Examples
Convert to meters:
5 km 5 hm 7 dam 
5,000 m + 500 m + 70 m = 5,570 m
3 m 2 cm 3 mm 3 m + 0.02 m + 0.003 m = 3.023 m
25.56 dam + 526.9 dm 255.6 m + 52.69 m = 308.29 m
53,600 mm + 9,830 cm 53.6 m + 98.3 m = 151.9 m
1.83 hm + 9.7 dam + 3,700 cm 183 m + 97 m + 37 m = 317 m
Other Measurements of Length
Other measurements of length are to measure very large distances, especially in astronomy:
Astronomical Unit
An astronomical unit is the mean distance from the Earth to the Sun. It is used in the measurement of orbits and trajectories inside the Solar system.
1 UA = 149,597,871 km
Light-year
The light-year is equal to the distance traveled by light in one average solar year. It is used in astronomy to measure extremely large distances.
The light-year is approximately equal to:
1 light year ≈ 9,461,000,000,000 km
Parsec
The parsec is an astronomical unit of measurement corresponding to the distance between the earth and an astronomical object with a parallax angle of one second.
The parsec is approximately equal to:
1 parsec ≈ 30,857,000,000,000 km
Microscopic Measurements:
Micrometre or Micron
It is equivalent to one millionth of one part meter.
1 μm = 0.000001 m
Nanometer
Equivalent to a billionth of a meter. Used to measure ultraviolet radiation, infrared radiation and light.
1nm = 0.000000001m
Angstrom
Equal to one ten-billionth of a meter (long short). It is the unit used primarily to express wavelengths, molecular and atomic distances.
1Å = 0.0000000001 m
