Stone (st)

Definition

Exactly 14 pounds — the imperial unit defined in Schedule 1 of the UK Weights and Measures Act 1985, so 1 st = 6.35029318 kg exactly.

History

The stone was a trading weight that varied by commodity and region across medieval Europe before Britain fixed it at 14 pounds. It is defined in Schedule 1 of the UK Weights and Measures Act 1985.

Where it is used

The stone is still the usual way to give body weight in the United Kingdom and Ireland, where a person might be eleven stone four, but it is little used elsewhere.

Typical uses include body weight in the UK and Ireland.

Conversion pages

These pages convert stone to or from another unit in weight.

• Stone to pound
• Kilogram to stone

Other Weight units

• Kilogram (kg)
• Gram (g)
• Pound (lb)
• Ounce (oz)
• Milligram (mg)
• Microgram (mcg)
• Tonne (t)

Sources

• UK W&M Act 1985 Weights and Measures Act 1985 (UK), Schedule 1, Part VI · Dataset reviewed Nov 11, 2026