TL;DR: Converting weight from stones (st) to kilograms (kg) is a direct calculation based on a fixed conversion factor.
- One stone is exactly 6.35029318 kilograms.
- The conversion formula is: kg = stones × 6.35029318.
- The stone is an imperial unit that is equal to 14 pounds (lbs).
- It is primarily used in the United Kingdom and Ireland to measure body weight.
- To convert kilograms to stones, divide the kg value by 6.35029318.
How Many Kilograms Are in One Stone?
One stone is equal to exactly 6.35029318 kilograms (kg). This value is the internationally agreed-upon standard for converting between these two units of mass. The stone is part of the imperial system of weights and measures and is defined as 14 avoirdupois pounds.
The kilogram equivalent is derived from the definition of the international pound, which is precisely 0.45359237 kg. Multiplying this value by 14 gives the exact kilogram value for one stone. For most everyday purposes, such as checking body weight, rounding the conversion factor to 6.35 kg provides a result that is accurate enough.
Stone to kg Conversion Formula and Examples
To convert a measurement from stones to kilograms, you multiply the number of stones by the conversion factor 6.35029318. The standard formula is: Kilograms = Stones × 6.35029318.
If a weight includes both stones and pounds, you must first convert the entire measurement into a single unit before converting to kilograms. The most common method is to convert the total weight into pounds (1 stone = 14 lbs) and then multiply the total pounds by 0.45359237 to get kilograms.
The table below shows common conversions from stones to their approximate kilogram equivalents.
| Stones (st) | Kilograms (kg) - Approx. |
|---|---|
| 1 st | 6.35 kg |
| 5 st | 31.75 kg |
| 10 st | 63.50 kg |
| 12 st | 76.20 kg |
| 15 st | 95.25 kg |
| 20 st | 127.01 kg |
Why Is the Stone Unit Used for Weight?
The stone is used for weight due to its long history as a unit within the English and later the British Imperial systems of measurement, primarily for trade. The name originates from the practice of using specific stones as weight standards in markets for centuries before measurement was formally standardized. The unit became legally defined for weighing agricultural goods like wool, potatoes, and spices.
The convention of one stone equalling 14 pounds was established for the wool trade in England during the Middle Ages. This standard eventually became widespread and has persisted into the modern era, where its use is now almost entirely limited to the colloquial measurement of human body weight.
Which Countries Still Use the Stone?
The United Kingdom and Ireland are the primary countries where the stone is still in common use as a unit of weight. In these nations, it is used almost exclusively for measuring a person's body weight in informal and personal contexts. People often state their weight in stones and pounds rather than in kilograms or just pounds.
Despite its popular use, the stone is not an official unit for commerce or administration in these countries. Medical records, scientific measurements, and official documentation exclusively use metric units, specifically the kilogram. In other Commonwealth nations like Canada and Australia, the stone is rarely used, though some older individuals may still be familiar with it. The United States does not use the stone, measuring body weight in pounds.
How to Convert Kilograms to Stones
To convert kilograms to stones, you divide the kilogram value by 6.35029318. The conversion formula is: Stones = Kilograms / 6.35029318. This calculation often results in a decimal number, which can be broken down into a combination of stones and pounds for a more conventional measurement.
For example, to convert 70 kg to stones and pounds:
- Step 1: Convert kg to decimal stones.
- Step 2: Identify the whole stones.
- Step 3: Convert the decimal part to pounds.
- Final Result: 70 kg is approximately 11 stone and 0.3 pounds.
Frequently Asked Questions
What is 10 stone in kg? 10 stone is equal to 63.50 kilograms. This is calculated by multiplying 10 by the conversion factor of 6.35029318.
What is 12 stone 5 lbs in kg? 12 stone 5 lbs is approximately 78.47 kg. To calculate this, first convert the entire weight to pounds (12 st × 14 lbs/st + 5 lbs = 173 lbs), then convert the total pounds to kilograms (173 lbs × 0.45359237 kg/lb).
Why are there 14 pounds in a stone? The standard of 14 pounds in a stone originates from medieval English trade practices, where it became a legally defined and convenient measure for commodities, most notably wool.
Is the stone an official unit of measurement? The stone is no longer an official unit for trade or administrative purposes in the UK or Ireland. It has been legally superseded by the kilogram, but its use persists informally and culturally for measuring personal weight.