Science
What Is Mass?
Definition, SI units, measurement, and how mass differs from weight — explained clearly.
Definition of Mass
Mass is a fundamental physical property that quantifies the amount of matter in an object. Unlike weight, which depends on gravity, mass remains constant everywhere in the universe.
SI Units of Mass
The base International System of Units (SI) unit for mass is the kilogram (kg). Since 2019, the kilogram is defined by fixing the numerical value of Planck's constant to exactly 6.62607015 × 10⁻³⁴ J·s.
Units
Units of Mass
| Unit | Symbol | Relation to Kg | System |
|---|---|---|---|
| Kilogram | kg | 1 kg (base SI unit) | SI / Metric |
| Gram | g | 1 g = 0.001 kg | SI / Metric |
| Milligram | mg | 1 mg = 0.000001 kg | SI / Metric |
| Pound | lb | 1 lb = 0.45359237 kg | Imperial / US |
| Ounce | oz | 1 oz = 0.0283495 kg | Imperial / US |
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