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What unit of measurement is used for mass?

We measure objects not only in physics or chemistry labs but in our day to day life. Whenever we are measuring any object we must measure it according to some predefined units which are standards for industry and scientific community. Let’s learn about some standard units of measurement for measuring mass. 

What unit of measurement is used for mass?

What unit of measurement is used for mass in physics?

A simple answer to this question can be Kg or pound. These are the most common units of mass we encounter in our day-to-day life. It must be noted that Kilogram is the SI unit and a pound is an imperial unit.

To convert from kg to pound, multiply the kg unit by 2.20462 (1 kg = 2.2 lb)

To convert from pound to kg, multiply the pound unit by 0.453592 (1 lb = 0.45 kg)

But the question arises are these the only units of measurement that are being used to measure mass?

The answer is no. There are several units of mass used in various systems of units. Also sometimes it depends on the object whose mass we are measuring. For example To measure the mass of a person we use units like Kg or lbs.

Different units used for measurement of mass

The United States customary units – pound (lb)

The United States customary units ( U.S. customary units ) are a system of measurements commonly used in the United States since it was formalized in 1832. The United States customary system ( USCS or USC ) developed from English units which were in use in the British Empire before the U.S. became an independent country. (en.wikipedia.org)

The unit for determining weight in the  U.S. Customary system is based on


  • “Ounce” basically means “Avoirdupois Ounce”. 
  • 28.349523125 gram is the same as Avoirdupois Ounce 
  • The abbreviation for ounce is “oz” and this word is derived from the 15th-century Italian word “onza”.
  • “Ounce” and “Fluid Ounce” are different. Students should not be confused between these two. Here Ounce is the unit for mass and Fluid Ounce is the unit for measuring volume.
  • An ounce is a unit used for measuring lighter objects like a piece of bread.
  • “Troy Ounce” is mostly used for measuring precious metals and gems. 31.1034768 gram is equivalent to  Troy Ounce.


  • lb is the abbreviation used for pound-mas is the basic unit for measuring mass in U.S. customary system. 
  • 1 pound is equal to 16 ounce
  • 1 lb = 0.45 kg
  • From humans to food to poultry, pounds are used to quantify a variety of items.


  • But we use another unit called tons if the object we are measuring is really big or very heavy.
  • 1 ton = 2,000 pounds
  • The tonnes instead of pounds are used to weigh trucks, ships, and heavy machinery. An elephant that is very heavy weighs around 7 tonnes.

Conversion between ounce pound and tons
1 pound = 16 ounces
1 ton = 2,000 pounds = 32,000 ounces

The International System of Units (SI Unit- Mass)

The kilogram is a cylinder of special metal about 39 millimeters wide by 39 millimeters tall that serves as the world’s mass standard. (nist.gov)

So, In the SI system or the metric system of unit Kilogram (Kg) is the standard unit of mass. Gram (g) is also a smaller unit of mass used in metric units. There are prefixes that we can use if we want to measure a large amount of mass in metric units.

In this system of the unit of weight is Newton (N) and is different from the unit used for measuring mass.

Atomic mass unit

If we are measuring the mass of subatomic particles we might employ another unit altogether, for example, a.m.u. (atomic mass unit). We can always perform a conversion between units where

a.m.u. (atomic mass unit) =1.6605×10−27kg

Please note that a.m.u. is not an SI unit.

The atomic mass unit (u) is 1/12 of the mass of a carbon 12 atom which is approximately 1.66 × 10 −27 kg. The atomic mass unit is convenient for expressing the masses of atoms and molecules. (en.wikipedia.org)

Since 1 a.m.u.  is exactly one-twelfth of the mass of a carbon-12 atom so, a carbon-12 atom has a mass of exactly 12 u. 

Scalars and Vectors in physics x
Scalars and Vectors in physics


Apart from Kg, pound, and a.m.u. there are many other units that are used to measure mass. The table given below shows some of the frequently used units of mass These are all different units used for measurement of mass and different units are employed depending on the object whose mass we are measuring.

For example, we often use grams as a unit of mass when we buy spices and we use kilograms while buying vegetables. It all depends on the quantity of mass in the object we are measuring. Metric Ton is a unit that is equivalent to 1,000 Kg. Now, this is a large unit and is used for measuring huge or massive objects. For example, if you want to measure the mass of a truckload of stones for construction of a building Metric Ton might be a better unit to use instead of gram or Kilogram

What we have discussed here are standard units of measurement of mass. Follow this link to learn about non standard units of measurement.

FAQs about unit of mass

What units can measure mass?
SI unit to measure mass is the gram, abbreviated as g.
1000 grams = 1 kg
1 t = 1000 kg.
1 pound = 0.45 kg.

What unit is used to measure weight?
In the U.S. Customary, the pound is the universal measure of weight, with two variations in common use and they are an ounce (1/16 pound) and a ton (2000 pounds).
In countries following the metric system, materials are generally specified not by weight but by mass, which is measured in grams or Kilograms, or in metric tons (1000 Kilograms). However, the unit for measurement of weight is Newton(N).

What is mass?
Mass is the amount of matter that an object possesses.

Is a gram a unit of mass?
Yes, it is a unit in the metric system.