Stones to Kilograms

About Stones and Kilograms

Stones (st): A British unit equal to 14 pounds (about 6.35 kg), originally for trade in raw materials by the stone (literally — large stones used for trade weights). Common uses: British body weight in casual conversation ('I weigh 11 stone 4'), still widely used in the UK and Ireland; not used in the US and rarely in other countries.

Kilograms (kg): The SI base unit of mass; defined since 2019 by the Planck constant, replacing a physical platinum-iridium artifact (Le Grand K) that had served as the definition for 130 years. Common uses: Body weight (everywhere except the US), shipping and freight, food packaging, athletics (Olympic lifts, international powerlifting), and any large-scale industrial measurement.

How the conversion works

Mass conversions use the SI definition: 1 pound is exactly 0.45359237 kilograms. The factor above is the exact ratio between stone and kilogram.

The exact relationship is kilograms = stones × 6.35029318, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.

When this conversion matters

Converting between stones and kilograms comes up wherever weight & mass measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.