What is stone?
A stone is a unit of mass used primarily in the United Kingdom and Ireland, equal to 14 pounds. It is mainly used to express human body weight in everyday conversation.
Real-world uses
The stone is used primarily in the UK and Ireland for expressing body weight (e.g., "I weigh 11 stone"). It appears on bathroom scales sold in Britain and is the preferred unit in British medical consultations for patient weight discussions.
History
The stone has been used in the British Isles since at least the 14th century for weighing agricultural goods. Its value varied historically (from 4 to 32 pounds depending on the commodity) before being fixed at 14 pounds by the Weights and Measures Act of 1835.
Common mistakes
Assuming a stone is used outside the British Isles—it is virtually unknown in the US, continental Europe, or most other countries. Also, forgetting that 1 stone = 14 pounds, not 10 or 12.
What is tonne?
A tonne, also known as a metric ton, is a unit of mass equal to 1,000 kilograms. It is used in industrial shipping, cargo measurement, and large-scale material production and trade.
Real-world uses
Tonnes (metric tons) are used globally for cargo shipping weights, industrial raw materials, agricultural harvest yields, and carbon emissions reporting. A standard shipping container might carry up to about 28 tonnes of cargo.
History
The tonne derives from the Old French "tonne" meaning a large cask. It was formalized in the metric system as exactly 1,000 kilograms. Though not an official SI unit, it is accepted for use with SI and is the global standard in trade.
Common mistakes
Confusing the metric tonne (1,000 kg) with the US short ton (907.18 kg) or the Imperial long ton (1,016.05 kg). Using "ton" ambiguously without specifying which system creates significant commercial errors.
When is this conversion used?
Converting between stone and tonne is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
Worked examples
1 stone = 0.00635029 tonne
1 tonne = 1,000 kilogram
How to convert stone to tonne
To convert stone to tonne, multiply the value by 0.00635029.
To convert tonne back to stone, multiply by 157.47304442.
Measurement standards
The kilogram is defined by fixing the Planck constant to exactly 6.62607015 × 10⁻³⁴ joule-seconds, as established at the 26th General Conference on Weights and Measures in 2018. This ended the last SI definition based on a physical artefact.
Did you know?
The International Prototype of the Kilogram, a platinum-iridium cylinder stored near Paris since 1889, was found to have drifted by about 50 micrograms relative to its copies over a century — roughly the mass of a fingerprint.
Quick reference: stone to tonne
| stone | tonne |
|---|---|
| 0.1 | 0.00063503 |
| 0.5 | 0.00317515 |
| 1 | 0.00635029 |
| 2 | 0.01270059 |
| 5 | 0.03175147 |
| 10 | 0.06350293 |
| 25 | 0.15875733 |
| 50 | 0.31751466 |
| 100 | 0.63502932 |
| 250 | 1.5875733 |
| 500 | 3.17514659 |
| 1,000 | 6.35029318 |
Common values
| stone | tonne | |
|---|---|---|
| A paperclip | 0.15747304 stone | 0.001 tonne |
| A smartphone | 27.55778277 stone | 0.175 tonne |
| A bag of sugar | 0.15747304 stone | 0.001 tonne |
| Average adult human | 11.02311311 stone | 0.07 tonne |
| A small car | 188.9676533 stone | 1.2 tonne |