The stone equals 14 pounds or 6.35 kilograms. It is used almost exclusively in the UK and Ireland to express human body weight. A 70 kg person is described as "11 stone" in British English. The stone is not used in trade, science or any other context.
Real-world: A 70 kg adult is about 11 stone. A British NHS weight chart marks stones alongside kg. A heavyweight boxer over 14 stone is typical.
Read full stone reference →The kilogram is the SI base unit of mass. Since 2019 it has been defined via the fixed numerical value of Planck's constant — a major shift from the previous definition based on a physical artifact. One litre of water at 4 °C has a mass of almost exactly 1 kg, a coincidence designed into the original 1795 definition.
Real-world: A litre of water weighs 1 kg at 4 °C. An average adult weighs 60–90 kg. A standard bag of flour is 1 kg.
Read full kilogram reference →