What is kilogram?
The kilogram is the SI base unit of mass. It is used globally as the standard for measuring weight and mass in science, industry, trade, and everyday life.
Real-world uses
The kilogram is the SI base unit of mass, used universally in science, commerce, and daily life outside the US. Grocery items, body weight in medical settings, and shipping weights are measured in kilograms across most of the world.
History
Originally defined in 1795 as the mass of one litre of water at 4°C. A platinum-iridium cylinder served as the standard from 1889 until 2019, when the kilogram was redefined in terms of the Planck constant, ending reliance on a physical artefact.
Common mistakes
Confusing mass (kg) with weight (newtons)—a kilogram measures mass, not force. Also, assuming 1 kg equals exactly 2 pounds; it is actually about 2.205 pounds.
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.
When is this conversion used?
Converting between kilogram and stone 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. Body weight, grocery items, and luggage limits are commonly expressed in kilograms in most countries and pounds in the US and UK, making this one of the most frequently needed mass conversions.
Worked examples
1 kilogram = 0.15747304 stone
1 stone = 6.35029318 kilogram
How to convert kilogram to stone
To convert kilogram to stone, multiply the value by 0.15747304.
To convert stone back to kilogram, multiply by 6.35029318.
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: kilogram to stone
| kilogram | stone |
|---|---|
| 0.1 | 0.0157473 |
| 0.5 | 0.07873652 |
| 1 | 0.15747304 |
| 2 | 0.31494609 |
| 5 | 0.78736522 |
| 10 | 1.57473044 |
| 25 | 3.93682611 |
| 50 | 7.87365222 |
| 100 | 15.74730444 |
| 250 | 39.3682611 |
| 500 | 78.73652221 |
| 1,000 | 157.47304442 |
Common values
| kilogram | stone | |
|---|---|---|
| A paperclip | 1 kilogram | 0.15747304 stone |
| A smartphone | 175 kilogram | 27.55778277 stone |
| A bag of sugar | 1 kilogram | 0.15747304 stone |
| Average adult human | 70 kilogram | 11.02311311 stone |
| A small car | 1,200 kilogram | 188.9676533 stone |