Stone vs Pounds
Stones and pounds — the British body-weight convention and how to read it
Understanding the differences between Stone (st) and Pound (lb) is essential for choosing the right system for your needs. This comparison covers the key differences, advantages of each approach, and practical guidance on when to use one over the other. Whether you are a student, engineer, scientist, or just curious about measurement systems, this guide will help you understand the trade-offs and make informed decisions.
Stone (st)
Exactly 14 pounds, or about 6.35 kg. Used almost exclusively in the UK and Ireland, and almost exclusively for body weight.
Pound (lb)
The base avoirdupois unit, exactly 0.45359237 kg. Used alone for body weight in the US.
Key Differences
- 1A stone is 14 pounds — not 10, not 16. The number is a survival of medieval wool trading, where different commodities had different stone weights before standardisation.
- 2British body weight is stated as stones AND pounds together: 11 stone 4 means 11*14 + 4 = 158 lb. The pounds component is always less than 14.
- 3American body weight is stated in pounds alone: the same person is 158 lb. Most of the rest of the world says 71.7 kg.
- 4The stone is essentially never used for anything except people. UK shops sell produce in kilograms, and UK freight is in kilograms or tonnes.
- 5Medical settings in the UK generally use kilograms, because drug dosing is per kilogram — so a British patient may know their weight in stones and be recorded in kilos.
Background
Before standardisation a stone varied by trade and by region — a stone of wool, a stone of meat and a stone of cheese were different weights, which suited merchants who dealt in only one commodity. The Weights and Measures Act of 1835 fixed it at 14 pounds for general use. Britain's incomplete metrication left it in place for the one purpose where people had the strongest personal attachment to the old numbers, which is why it survives for body weight and essentially nothing else.
When to Use Stone (st) vs Pound (lb)
Use Stone (st) when…
Use stones and pounds when talking about body weight with a British or Irish audience. It is what people know their own weight in, and converting for them usually adds friction rather than clarity.
Use Pound (lb) when…
Use pounds alone for a US audience, and kilograms for medical, scientific or international contexts — including UK medical records.