Common mathematical length units are as follows:

The traditional length units in China are Li, Zhang, ruler, inch and so on. Other length units include: light year, meter (Pm), megameter (mm), kilometer (km), decimeter (dm), centimeter (cm), millimeter (Mm), Simi (dmm), Mi Hu (cmm) and so on.

1 light-year = 9.46 ×10/5 m (light-year)1pm =1×10/5 m (m)1mm. DM =1×10 (-1) m (decimeter)1cm =1×10 (-2) m (cm)1mm.

1 DMM =1×10 (-4) m (sago)1CMM =1×10 (-5) m (Mi Hu)1. M (nano)1pm =1×10 (-12) m (picometer)1FM =1×10 (-/kloc

In addition, a unit Egstrom (abbreviated as Egstrom, symbol? ) is a unit of length. It is not SI unit, but it can be converted by SI unit, that is,1a =10 (-10)1m = 0.1nm.

A few European and American countries, mainly Britain and the United States, use English units, so they use different length units.

There are mainly miles, yards, feet and inches. Miles 1 mile = 1760 yards =5280 feet = 1.609344 kilometers yards (yards, yd) 1 yards =3 feet =0.9 144. Fa) 1 fathom =2 yards = 1.8288 meter wave (furlong)/wave 220 yards = 20 1. 1 7 meter feet (feet, ft, plural feet)/kloc-0.

Astronomy often takes "light year" as the unit of length, which is the distance traveled by light in vacuum 1 year, so it is called light year. 1 light year 9.4653× 10 12km, but traditionally, light year is the unit of distance. Another commonly used unit of length is the parsec. Refers to the distance with annual parallax of 1 sec. 1 parsec =3.26 16 light years. In addition, there is a commonly used length unit "astronomical unit". 1 astronomical unit ≈ 65438+496 million kilometers.