What Is a Stone in Weight? Definition, History, and Conversions

4 min read•June 2, 2026•Reviewed: June 2, 2026

✓Reviewed by Apex Conversion Editorial Team · Last reviewed June 2, 2026

A stone is a unit of weight equal to exactly 14 pounds or 6.35029 kilograms. It is used almost exclusively in the United Kingdom and Ireland for expressing body weight in informal conversation. Unlike most measurement units, the stone has no official SI status and is rarely used outside these two countries — or outside the specific context of body weight.

In the UK, bathroom scales often display weight in stone and pounds simultaneously. A person might say they weigh '11 stone 4' meaning 11 stones plus 4 extra pounds, for a total of 11 × 14 + 4 = 158 pounds = 71.7 kg. This combined format is the standard way to express body weight in everyday British conversation.

Stone Conversion Formulas

stone → lb:   lb  = st × 14    (exact)
stone → kg:   kg  = st × 6.35029
lb    → stone: st = lb ÷ 14
kg    → stone: st = kg ÷ 6.35029

For X stone Y pounds:
  Total lb = (X × 14) + Y
  Total kg = ((X × 14) + Y) × 0.453592

Common body weight values:
   8 st  = 112 lb  = 50.8 kg
  10 st  = 140 lb  = 63.5 kg
  12 st  = 168 lb  = 76.2 kg
  14 st  = 196 lb  = 88.9 kg

Where Is Stone Used?

The stone is officially legal for use in the UK and Ireland but is not an SI unit and is not recognized in international trade. In practice, it survives mainly for body weight discussions in the UK and Ireland. NHS medical records, UK GP practices, and British media typically use both kg and stone/pounds. Younger generations in the UK are increasingly comfortable with kg as the UK continues metric transition.

The stone is not used in the United States, Canada, Australia, or anywhere else in the world. If you see a weight expressed in stone outside of British or Irish context, it is almost certainly a conversion from one of those two countries. For international specifications, products, and scientific work, kilograms are always used.

Frequently Asked Questions

How many pounds is 1 stone?

Exactly 14 pounds. This is a fixed definition — 1 stone = 14 lb with no rounding or approximation.

How many kilograms is 1 stone?

1 stone = 14 lb × 0.453592 = 6.35029 kg.

What countries use stone for weight?

Primarily the United Kingdom and Ireland for body weight in informal conversation. No other country uses stone as a standard weight unit.

How do I convert stone to kg?

Multiply stone by 6.35029. Example: 10 st × 6.35029 = 63.50 kg. Alternatively, multiply stone by 14 to get pounds, then multiply by 0.453592 to get kg.

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