Length, area, volume, volume and mass are important components of the international system of units.

Commonly used conversion relationships are:

1, length unit:

1 km (km) = 1 0,000m (m) =100,000m (cm) = 1 0,000mm (mm);

2. Area unit:

1 ㎡( 1㎡)= 100dm？ (100 square decimeter) = 10000 cm? ( 10000 cm2)= 1000000mm？ (1000000 mm2) = 0.0001hectare =0.00000 1km? (0.000001km2) = 0.01hectare = 0.00044 1054 acre = 0.00 1 square mile =10+038.

3. unit of volume:

1 m3 = 1000 liter = 1000 cubic decimeter = 1 000,000 ml = 1000000 cubic centimeter = 1 000000 cubic millimeter.

4. unit of volume:

1 liter = 1 decimeter cubic = 1000 ml = 1000 cubic centimeter = 1 000,000 cubic millimeter.

5, quality unit:

1 kg = 0.00 1 ton = 1, 000 g = 1, 000,000 mg = 1, 000,000 micrograms.