Kilogram(kg)
The kilogram (kg) is the SI base unit of mass. It is the only SI base unit still defined by a physical artifact in the historical form, and the current SI definition fixes the Planck constant.
Reviewed
- Symbol
- kg
- Quantity
- Mass
- Measurement system
- SI
- SI classification
- SI base unit
- Reference unit
- SI base unit for mass
- Exact relationship
- 1 kg = 1,000 g exactly
What the kilogram is
The kilogram is the SI base unit of mass. It is the standard unit used for everyday weights, scientific measurements, and many industrial applications.
SI definition and modern precision
The kilogram was historically defined by a physical artifact, but the 2019 SI revision redefined it using the fixed numerical value of the Planck constant. This keeps the unit consistent and independent from a single metal object.
How it relates to other units
The kilogram is the basis for the decimal SI mass system. Common subdivisions include the gram, milligram, and tonne, while larger units such as the metric ton are defined in multiples of kilograms.
- 1 kilogram = 1,000 grams
- 1 gram = 0.001 kilogram
- 1 tonne = 1,000 kilograms
Everyday use
Kilograms are used in grocery shopping, body weight, shipping, science labs, and a wide range of engineering calculations. It is a universal practical unit for mass in most countries and in the SI.