Mass Converter
Convert mass units from micrograms to solar masses.
Enter a value, choose the units, and see the result plus every other mass unit.
Kilogram → Pound (avoirdupois)
Mass Converter
Mass spans more than 60 orders of magnitude, from a single electron to an entire star. This converter covers that full range in one table, with SI units alongside the troy system used for precious metals and the constants physicists and astronomers rely on.
Units included
- SI: tonne, kilogram, gram, milligram, microgram, nanogram.
- Avoirdupois: pound and ounce.
- Troy: troy pound, troy ounce, pennyweight.
- Engineering: slug.
- Physics: atomic mass unit (dalton), electron mass.
- Astronomy: Earth mass, solar mass.
Mass is not weight
Mass measures how much matter an object contains, while weight is the force gravity exerts on it. An astronaut of 80 kg still has 80 kg of mass on the Moon, even though a spring scale would read about one sixth as much. For converting kg, pounds, and stone in everyday settings, the Weight Converter is simpler; for forces in newtons use the Force Converter.
Precious metals: the troy system
Gold, silver, and platinum prices are quoted per troy ounce, not per regular ounce.
| Unit | Grams | Relation |
|---|---|---|
| Pennyweight | 1.55517384 | 1/20 troy oz |
| Troy ounce | 31.1034768 | 1.0971 avoirdupois oz |
| Troy pound | 373.2417216 | 12 troy oz |
Worked example: a 100 g gold bar holds 3.2151 troy ounces, and a 1 kg bar holds 32.1507 troy ounces – multiply by the spot price per ounce to value it.
Atomic and astronomical scales
Chemists work in daltons: a water molecule of 18.015 u has a mass of about 2.9915e-26 kg. One atomic mass unit equals about 1,822.89 electron masses. At the other extreme, the Sun has a mass of 1.98847e30 kg, which is about 332,954 Earth masses. Very large or small results are shown in scientific notation so no digits disappear, and the precision selector lets you choose how many decimals to keep.
Frequently Asked Questions
What is the difference between mass and weight?
Mass is the amount of matter in an object and is measured in kilograms; it is the same everywhere. Weight is the gravitational force on that mass and is measured in newtons, so it changes on the Moon while the mass does not.
Is a troy ounce heavier than a regular ounce?
Yes. A troy ounce is 31.1034768 g while an avoirdupois ounce is 28.349523125 g, so one troy ounce is about 1.0971 regular ounces. A troy pound, however, has only 12 troy ounces and is lighter than an avoirdupois pound.
What is an atomic mass unit?
The atomic mass unit, or dalton (u), is one twelfth of the mass of a carbon-12 atom, about 1.66053906892e-27 kg. A proton or neutron is roughly 1 u, and an electron is about 1/1823 u.
What is a slug?
The slug is the mass unit of the US engineering system. One pound-force accelerates one slug at 1 ft/s², which makes a slug about 14.5939 kg or 32.174 pounds.