Popular conversions
13 pairsKilogram ↔ Gram
kg ↔ g
Gram ↔ Milligram
g ↔ mg
Kilogram ↔ Pound
kg ↔ lb
Tonne ↔ Kilogram
ton ↔ kg
Gram ↔ Ounce
g ↔ oz
Pound ↔ Ounce
lb ↔ oz
Okka ↔ Gram
okka ↔ g
Okka ↔ Kilogram
okka ↔ kg
Dirham ↔ Gram
dirhem ↔ g
Okka ↔ Dirham
okka ↔ dirhem
Byzantine Litra ↔ Gram
litra ↔ g
Byzantine Litra ↔ Byzantine Ounce
litra ↔ ounkia
Byzantine Ounce ↔ Gram
ounkia ↔ g
Unit guides
6 unitsDetailed guide to Mass
Mass is a physical quantity associated with the amount of matter and the inertia of an object. The kilogram is the base unit of mass in the International System of Units.
Mass units are used in science, engineering, commerce, medicine, manufacturing and everyday measurements. Metric units use decimal relationships, while units such as the pound belong to imperial and United States customary systems.
- Physical quantity
- Mass
- SI base unit
- Kilogram
- SI symbol
- kg
- Dimension symbol
- M
- Modern definition
- Defined by fixing the numerical value of the Planck constant
What is mass?
Mass is a fundamental physical quantity related to an object's resistance to acceleration. It also acts as a source of gravitational interaction.
In dimensional analysis, mass is represented by M. It appears in derived quantities such as density, momentum, force, pressure and energy.
Mass and weight are not the same
Mass describes an intrinsic property of an object, while weight is the gravitational force acting on that mass. The mass of an object remains the same when its location changes, but its weight can vary with gravitational acceleration.
In the International System of Units, mass is measured in kilograms and force is measured in newtons. Everyday language often uses the word weight when technically referring to mass.
The kilogram as the SI base unit
The kilogram is the SI base unit of mass. Unlike the names of most base units, its name already contains the metric prefix kilo.
Since 2019, the kilogram has been defined by fixing the numerical value of the Planck constant. This replaced the earlier definition based on a physical metal prototype.
Metric mass units
One kilogram equals 1,000 grams. One gram equals 1,000 milligrams, so one kilogram equals one million milligrams.
Grams are commonly used for food and laboratory materials, while milligrams are suitable for medicines, chemicals and other small quantities.
The pound and other non-metric units
The pound is used in the imperial and United States customary measurement systems. One international avoirdupois pound is exactly 0.45359237 kilograms.
The lb symbol originates from the Latin word libra. Because several historical pound definitions existed, modern calculations should use the standardized international pound.
How are mass units converted?
A mass conversion preserves the physical mass while expressing it with another unit. The numerical value is multiplied by the defined relationship between the source and target units.
Metric mass conversions use decimal factors. Converting between kilograms and pounds requires the exact relationship of one pound to 0.45359237 kilograms.
Measuring mass accurately
Mass is measured with balances and scales designed for different capacities and precision levels. Laboratory balances may detect milligram or microgram differences, while industrial scales measure much larger loads.
Reliable measurements require appropriate calibration, stable environmental conditions and correct handling of the measured material.
Mass units
| Unit | Symbol | Information |
|---|---|---|
| Kilogram | kg | View unit guide |
| Gram | g | View unit guide |
| Milligram | mg | View unit guide |
| Pound | lb | View unit guide |
| Tonne | t | View unit guide |
| Ounce | oz | View unit guide |
Sources
The definitions and conversion relationships on this page are aligned with standard metrology and SI reference material.