Metric units is one of the important topics of the mathematics. Metric unit trace their origin to the decimal system of measurement introduced in France in 1799. The term is now used as a synonym for "SI" (International System of Units) and is an official system of measurement everywhere. The main feature of the metric system was the standard set of inter-related base units and a standard set of prefixes in powers of ten.

Metric unit is a decimal unit of measurement of the metric system. In the metric system other units of measurement are obtained by multiplying and dividing by powers of 10.
Metric units system has some basic units:
  • m the meter for length
  • Kg the kilogram for mass
  • s the second for time
  • L the liter for Volume
Quantity Measured: Length, width, distance, and thickness.

Unit Symbol Relationship
Millimeter mm 100mm = 1cm
Centimeter cm 100cm = 1m
Kilometer km 1km = 1000m

The "meter" is the base unit of length.

The metric measurement is a system of measuring. Mass is a measure of the amount of material contained in an object. The gram is used to measure mass or weight.

Quantity Measured: Weight

Unit
Symbol
Relationship
Milligram mg 1000mg = 1g
Kilogram kg 1kg = 1000g
Metric ton t 1t = 1000kg = 1000000g

Capacity is the amount a container can hold. The SI unit of capacity is liter. 1 liter is equal to 1000 milliliter(mL), which is used to measure the capacities of larger containers. Milliliter is also a metric unit where it measures the capacities of small containers.

Quantity Measured: Volume

Unit
Symbol
Relationship
Milliliter mL 1000mL = 1L
Cubic centimeter C$m^{3}$ 1C$m^{3}$ = 1mL
Liter L 1000L = 1$m^{3}$


Solved Examples

Question 1: How many milliliters are in a 5-liter bottle?
Solution:
 
Here we need to change from a larger unit of volume to a smaller unit of volume.

As we know, 1L = 1000mL

So, 5L = 5000ml (5 $\times$ 1000 = 5000)
 

Question 2: 72000 grams will give you how many kilograms?
Solution:
 
72000grams = ___ Kg
          72000 grams = $\frac {72000}{1000}$ kg  (1 grams = $\frac{1}{1000}$)
                = 72 kg
 

Question 3: How do you convert 365,220 Centimeters to Kilometers?
Solution:
 
There are 100 cm in a meter and 1000 meters in a kilometer.

365220 cm * $\frac{1 meter}{100 cm} * \frac{1km}{1000 meters}$

=$\frac{365220}{100000}$
km

= 3.6522 km