What is a Stone? UK Weight Unit Explained

June 7, 2025 • 4 min read

If you have ever spoken to someone from the UK about their weight, you may have heard them say something like "I weigh 11 stone 4." For much of the world, this unit sounds archaic or confusing. Here is everything you need to know about the stone as a unit of weight.

How Much is a Stone?

The stone (abbreviated "st") is a traditional British unit of weight equal to exactly 14 pounds or approximately 6.35 kilograms. It is used almost exclusively in the UK and Ireland for measuring body weight.

Converting Stones to Other Units

To convert from stones to other units:

• ▶ Stones to pounds: multiply by 14
• ▶ Stones to kilograms: multiply by 6.35
• ▶ Pounds to stones: divide by 14
• ▶ Kilograms to stones: divide by 6.35

Example: 12 stone 7 lbs = (12 × 14) + 7 = 175 lbs = 79.4 kg

Common Body Weights in Stones

• ▶ 8 stone = 112 lbs = 50.8 kg
• ▶ 10 stone = 140 lbs = 63.5 kg
• ▶ 11 stone = 154 lbs = 69.9 kg
• ▶ 12 stone = 168 lbs = 76.2 kg
• ▶ 13 stone = 182 lbs = 82.6 kg
• ▶ 15 stone = 210 lbs = 95.3 kg

Why Does the UK Still Use Stones?

Britain officially adopted the metric system in 1965, but old habits die hard. The stone persists in everyday conversation for several reasons:

• ▶ Cultural habit — generations grew up using stones, and parents teach children what they know
• ▶ Convenient scale — whole stone numbers are easier to remember than three-digit pound or kilogram values
• ▶ Media reinforcement — British newspapers and TV still report celebrity weights in stones
• ▶ NHS influence — while doctors use kg, many GP scales display both

History of the Stone

The stone dates back to at least the 14th century when it was used for weighing agricultural commodities. Before standardisation, a "stone" varied by region and product — a stone of wool weighed differently from a stone of meat. In 1824, the British Weights and Measures Act fixed it at exactly 14 pounds.

Today, the stone is not recognised as an official SI unit and is rarely used outside the UK and Ireland. If you are travelling or communicating internationally, converting to kg or lbs will be better understood.