Weight/Mass Conversions
Popular Comparisons
| g | kg | oz | lb | st | |
|---|---|---|---|---|---|
| Paperclip | 1 | 0.001 | 0.035 | 0.002 | — |
| Smartphone | 200 | 0.2 | 7.05 | 0.441 | — |
| 1 litre of water | 1,000 | 1 | 35.27 | 2.205 | 0.157 |
| Average adult | 70,000 | 70 | 2,469 | 154.3 | 11.02 |
| Small car | 1,200,000 | 1,200 | 42,329 | 2,646 | 189 |
Weight/Mass
Mass and weight are related but distinct concepts in physics. Mass is a scalar quantity that measures the amount of matter in an object, expressed in kilograms (kg) in the SI system. Weight, by contrast, is the gravitational force acting on that mass, measured in newtons (N). In everyday language the two terms are used interchangeably, but the distinction is essential in physics: an astronaut in orbit is weightless but retains their full mass.
The kilogram is the SI base unit of mass and has one of the most fascinating definitions in all of science. From 1889 to 2019, it was defined by a physical platinum-iridium cylinder — the International Prototype of the Kilogram — stored in a vault outside Paris. In 2019, the kilogram was redefined using Planck's constant (h = 6.62607015 × 10⁻³⁴ J·s), making it the first base unit tied to a fundamental constant of nature rather than a physical object.
The imperial system uses pounds and ounces for everyday mass measurement, while the troy system — used for precious metals and gemstones — defines a troy ounce as 31.1035 grams, slightly heavier than the common avoirdupois ounce of 28.3495 grams. Chemistry and pharmacy routinely work in milligrams and micrograms, where even small conversion errors can have serious consequences in dosage calculations.