What is kilogram?
The kilogram is the SI base unit of mass. It is used globally as the standard for measuring weight and mass in science, industry, trade, and everyday life.
Real-world uses
The kilogram is the SI base unit of mass, used universally in science, commerce, and daily life outside the US. Grocery items, body weight in medical settings, and shipping weights are measured in kilograms across most of the world.
History
Originally defined in 1795 as the mass of one litre of water at 4°C. A platinum-iridium cylinder served as the standard from 1889 until 2019, when the kilogram was redefined in terms of the Planck constant, ending reliance on a physical artefact.
Common mistakes
Confusing mass (kg) with weight (newtons)—a kilogram measures mass, not force. Also, assuming 1 kg equals exactly 2 pounds; it is actually about 2.205 pounds.
What is tonne?
A tonne, also known as a metric ton, is a unit of mass equal to 1,000 kilograms. It is used in industrial shipping, cargo measurement, and large-scale material production and trade.
Real-world uses
Tonnes (metric tons) are used globally for cargo shipping weights, industrial raw materials, agricultural harvest yields, and carbon emissions reporting. A standard shipping container might carry up to about 28 tonnes of cargo.
History
The tonne derives from the Old French "tonne" meaning a large cask. It was formalized in the metric system as exactly 1,000 kilograms. Though not an official SI unit, it is accepted for use with SI and is the global standard in trade.
Common mistakes
Confusing the metric tonne (1,000 kg) with the US short ton (907.18 kg) or the Imperial long ton (1,016.05 kg). Using "ton" ambiguously without specifying which system creates significant commercial errors.
When is this conversion used?
Body weight, grocery items, and luggage limits are commonly expressed in kilograms in most countries and pounds in the US and UK, making this one of the most frequently needed mass conversions.
Worked examples
1 kilogram = 0.001 tonne
1 tonne = 1,000 kilogram
How to convert kilogram to tonne
To convert kilogram to tonne, multiply the value by 0.001.
To convert tonne back to kilogram, multiply by 1,000.
Measurement standards
The kilogram is defined by fixing the Planck constant to exactly 6.62607015 × 10⁻³⁴ joule-seconds, as established at the 26th General Conference on Weights and Measures in 2018. This ended the last SI definition based on a physical artefact.
Did you know?
The International Prototype of the Kilogram, a platinum-iridium cylinder stored near Paris since 1889, was found to have drifted by about 50 micrograms relative to its copies over a century — roughly the mass of a fingerprint.
Quick reference: kilogram to tonne
| kilogram | tonne |
|---|---|
| 0.1 | 0.0001 |
| 0.5 | 0.0005 |
| 1 | 0.001 |
| 2 | 0.002 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
| 250 | 0.25 |
| 500 | 0.5 |
| 1,000 | 1 |
Common values
| kilogram | tonne | |
|---|---|---|
| A paperclip | 1 kilogram | 0.001 tonne |
| A smartphone | 175 kilogram | 0.175 tonne |
| A bag of sugar | 1 kilogram | 0.001 tonne |
| Average adult human | 70 kilogram | 0.07 tonne |
| A small car | 1,200 kilogram | 1.2 tonne |