Convert Stones to Kilograms

About converting Stones to Kilograms

Stones (st) and Kilograms (kg) are both units of weight & mass, so converting between them is a single multiplication: multiply your Stones figure by 6.3503. Ten Stones comes to 63.5029 Kilograms, and a hundred works out at 635.0293 Kilograms.

Rule of thumb: going from Stones to Kilograms multiplies, so the figure always grows — one Stone is already 6.3503 Kilograms. If your answer came out smaller, you have the conversion the wrong way round.

What is a Stone?

The stone is fourteen pounds and, outside Britain and Ireland, essentially extinct. There it is still how people state body weight: a Briton says "eleven stone four", meaning eleven stone plus four pounds, and the plural stays stone in that construction — never "eleven stones". Americans give the identical weight as a single number in pounds, which is why British figures baffle them. The unit predates standardisation and was once a moving target, with a stone of wool, cheese or glass all weighing different amounts, and it is no longer permitted for trade in the UK at all.

What is a Kilogram?

The kilogram was the last SI unit still defined by a physical object — the International Prototype Kilogram, a platinum-iridium cylinder kept in a vault near Paris since 1889. The problem was that it drifted. Careful comparisons against its official copies showed the masses diverging by tens of micrograms, and because the prototype simply was the kilogram by definition, there was no way to say which side had changed. In 2019 it was redefined in terms of the Planck constant, so any properly equipped lab can now realise a kilogram from physics rather than from an artefact.

To put both in perspective: most adults weigh somewhere between 9 and 14 stone, while a liter of water weighs about a kilogram.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Kilograms to Stones converter, or browse all Weight & Mass converters.