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Kilogram (kg)

Quantity: Mass · Category: SI base

The kilogram is the SI base unit of mass. Since 2019 it has been defined by the Planck constant: fixed at exactly 6.62607015×10⁻³⁴ J·s, which anchors the kilogram to quantum physics instead of a physical metal cylinder kept in a vault.

Relation to SI

Base unit — defined via h = 6.62607015×10⁻³⁴ J·s exactly

Examples

  • A liter of water has a mass of about 1 kilogram.
  • An adult human is typically 60–90 kilograms.