It was the 19^{th} century when a scientist James Clerk Maxwell put forwarded the concept of a consistent system where the fundamental small units were the base and the rest were derived from them. This coherent system was the metric system with almost all of the dimensions either based or derived from the ratios of the base dimensions.

This wonderful system got popular in the whole world in just a century and in the 20^{th} century, it was adopted by almost all the world except a very few countries who were still reluctant and decided to stay on the conventional imperial system.

In the 19^{th} century, there were so many problems of solving the newly researched work due to the limitations of the imperial system, the metric system provides solutions for all those problems. Thus a quick transition took place from the conventional imperial unit system to the metric unit system.

Currently, the metric system also spreads to the whole world including 192 countries are using the imperial unit system while there are only 3 countries USA, Myanmar, and Liberia who are committed to staying on the imperial system.

The metric unit system is based on the seven base units including meter, kilograms, second, ampere, kelvin, candela, and mole. All of the base units were defined on the standards based on the natural dimensions of the earth. The rest of the units defined in these systems are either directly or indirectly derived from the ratios of the base units or dimensions.

The unit of mass (kilogram) was based on the mass of the one-liter cube (cubic decimeter) volume of water. The unit of time was taken as second in this system. The unit of length (meter) was based on the length of the path traveled by the light in the vacuum in the 1/299,792,458^{th} part of a second. The rest of the units were derived from the ratios of these defined fundamental units.

The metric unit system has a very wide range of base and derived units. The base units include a meter for length, kilogram for mass, second for time, ampere for electromagnetism, kelvin for temperature, candela for luminous intensity, and mole for quantity. The derived units include volt, ohm, tesla, weber, farad, henry, siemens, coulomb, watt, newton, joule, pascal, becquerel, sievert, gray, lux, and lumen.

The metric unit system can be converted to the imperial unit system using the following conversion coefficients. One meter to 3.28 Foot, one kilogram to 2.20 pound, one Kilometer to 0.62 Mile, one Kilometer to 3280.8 Feet, one Centimeter to 0.39 Inches, one Millimeter to 0.039 Inches, one Liter to 1.057 Quart, one Liter to 0.0264 Gallon, one Milliliter to 0.0042 Cups, one Milliliter to 0.0338 Ounce, one Celsius to °C x 9/5 + 32 = °F Fahrenheit, one Kilogram to 0.0011 Ton, one Gram to 0.035 Ounce, one Gram to 0.002205 Pound, and one Milligram to 0.000035 to Ounce.