Difference Between MG and MCG


Main Difference

There are several units of measurement that have their calculations. Then there are some units that are derived from the central unit to maintain a proper system to calculate things. It, therefore, the case with the one that is being discussed in this article and are known as MG and MCG which are sub-units of the main one called gram. The main difference between them is that MG is used to calculate the weight of smaller things that are minute whereas MCG is used to calculate even more minor things that are not even visible to the naked eye.

Comparison Chart

The thousand part of a gram.One thousand-thousandth part of a gram.
mgmcg or μg.
Kilogram Relation
The one millionth part of a kilogram.The one billionth part of a kilogram.
Mostly used to measure small weights that can include the ones of paper, liquid, and even tablets.Mostly used to calculate the weight of medical terms.
Ease of Use
Commonly used around the world and is one of the most used ones.Not that much used because of the confusion that can arise because of the unit mixture.
Small visible weightsMinute weights


MG that is also known as Milligram in simple words can be defined as a measurement that is equal to 10 raised to the power 3 of a gram. It can be said that a milligram is the one-thousandth part of a gram and is a unit that is used to measure mass in various forms. It is not the main unit, therefore has specific places where it can fully have the benefits. Most of the times it is used to calculate weights that are relatively small. This term can include a shopping bag, cork, a paper and some tablet. These show that the measurement is small and for all the things that have smaller weights, this is the one that is the standard. Since it has originated from the term gram, that defines itself as “the absolute weight of a volume of pure water equal to the cube of the hundredth part of a meter, and at the temperature of melting ice,” this shows that a millimeter will be 0.1 millionth part of a meter. According to few sources currently, it is the most used unit in the world which not only has utilization for things that are matristic but also for different kinds of liquids that include syrups and injections. This action can complete when we convert the actual unit from the main ones. After multiplying 0.001 by 1,000, the answer is 1. Liters multiplied by grams per liter become grams. This term will mean that a milliliter of water at its normal density of 1,000 kilograms per cubic meter will be equal to 1 gram or 1,000 milligrams. It means that we will have to know the actual density of the original substance. All in all, this is a unit which lies between the bigger and smaller ones to help the scientists or engineers in managing the calculations properly.



Although it is a small unit, and mostly not known by people who are not related to the field, MCG commonly used in medicine as the measurer. Showing how it refers to the other units within the system, we can say that it is a unit of mass that will be equal to a thousand times of a gram. This statement shows that it will be one million times smaller than a gram and from this, we can conclude that it is one billionth of a kilogram. This unit is such a small one that usually in real life there is no application of this; people do not measure things that are so small, and there are no proper units to do so. If we talk about the units, then μ is the symbol which ha uses for micro and gram stays as it is so it become μg. Most of the times it is used for food elements that are smaller in size or the internal organs and parts which are minuscule in weight and require a smaller unit to help in finding more about them. This fact is also the case with medicines that are given by the doctor. Another reason why it is not common is that the medical associations of most countries have recommended that this should not have a presence in front of any dose and other nutrition values. Since it can be confused with other units such as micro and milli- that can mean an increase of almost 1000% in the actual medicine that has a doctor prescription. Another place where it has benefits is when we talk about millie centigram; that is equal to 10 μg.

Key Differences

  1. Both the units have a derivation from the main one that is gram, which itself is the unit of a kilogram.
  2. MG is the thousand part of a gram whereas MCG is the one thousand-thousandth part of a gram.
  3. Regarding kilogram, MG is the one-millionth part of a kilogram whereas MCG is the one billionth part of a kilogram.
  4. The term MG is mostly used to measure small weights which can include the ones of paper, liquid, and even tablets. The term MCG is primarily used to calculate the weight of medical conditions.
  5. The term MG is commonly used around the world and is one of the most used ones whereas the term MCG has no proper usage because of the confusion that can arise because of the unit mixture.
  6. The main way of expressing MG regarding symbol is mg whereas the main way of expressing MCG is either mcg or μg.
Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss