Mass or Weight?
Mass and weight are different. Mass means how much matter is in an object. Weight is the measure of the force of gravity on that object.
For example, your body mass is the same on earth, on moon or on Jupiter but if you weigh 100 kilograms on earth, you weigh 16.6 kilograms on the moon and 236.4 kilograms on Jupiter because their gravities are different than earth.
The mass units in the converter:
"carat (ct), centigram, decigram, dekagram, dram, grain, gram (g), hectogram (hg), hundredweight, kilogram (kg), kiloton, megagram, megatonne, microgram, milligram (mg), nanogram, ounce (oz), petagram, picogram, pound (lb), quarter, stone (st) and ton"
Metric Mass Units
Because the metric system is a decimal system, all other metric mass units are either the fractions or the multiples of kilogram. The most frequently used metric mass units are kilogram (kg), gram (g) and milligram (mg).
The base unit of mass in the metric system is kilogram. Here is a quick reference list for the base metric mass unit, kilogram:
- 1 kilogram = 1000 grams
- 1 kilogram = 2.20462 pounds
- 1 kilogram = 35.274 ounces
- 1 kilogram = 0.157 stone
- 1 kilogram = ^{1}⁄_{1000} metric ton
Kilogram Definition (Before May 2019):
Kilogram is equal to the mass of the international prototype (platinum-iridium cylinder kept in France) of the kilogram. The kilogram prototype is also known as "Le Grand K".
Kilogram Redefinition (After May 2019):
On 16 November 2018, for the most accurate measurement, the scientists agreed that the SI base unit definitions should not be based on the physical objects but instead based on fundamental constants of nature that does not change over time, such as Planck constant etc.
With the new definition, the Kibble balance will be used to measure the mass of the kilogram. When you place a weight on the Kibble balance, the machine produces an electric current proportional to Planck’s constant. With Planck’s constant set, the kilogram will correspond to a specific amount of current in the Kibble balance.
Based on this, the redefinition of kilogram is:
"Kilogram is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs."
With the new definition, the kilogram also depends on the definitions of the second and the metre.
Imperial and US Customary Mass Units
In the imperial and the US Customary system the fundamental unit of mass is pound (lb). All other units are either the fractions or the multiples of pound.
The imperial and the US Customary system share the same mass units and only difference is with the hundredweight (112 pounds in imperial system and 100 pounds in US Customary system ) and the ton (2240 pounds in the imperial system and 2000 pounds in the US Customary system).
Here is the list of the Imperial and the US Customary mass units:
- grain (gr) = ^{1}⁄_{7000} pound
- drachm (dr) = ^{1}⁄_{256} pound
- ounce (oz) = ^{1}⁄_{16} pound
- pound (lb)
- stone (st) = 14 pounds
- quarter (qtr) = 28 pounds
- hundredweight (cwt) = 112 pounds in imperial, 100 pounds in US Customary
- ton (t) = 2240 pounds in imperial, 2000 pounds in US Customary