To convert stone to kilograms (st to kg), multiply by 6.3502932. 1 stone equals 6.3502932 kg, about 1.4 times as much as a house cat.
| stone | kilograms |
|---|---|
| 1 stone | 6.3502932 kg |
| 2 stone | 12.700586 kg |
| 5 stone | 31.751466 kg |
| 10 stone | 63.502932 kg |
| 25 stone | 158.75733 kg |
| 50 stone | 317.51466 kg |
| 100 stone | 635.02932 kg |
| 250 stone | 1,587.5733 kg |
| 500 stone | 3,175.1466 kg |
| 1000 stone | 6,350.2932 kg |
Definition: 14 pounds, or about 6.35 kilograms.
History: Started as exactly what it sounds like: a stone used as a physical weight on a scale. Different regions of England once had wildly different "stones," ranging anywhere from 5 to 40 local pounds depending on what was being weighed and where. The 14-pound version was formally fixed into English law in 1835, well after most other regional stones had already been standardized away.
Current use: Almost exclusively body weight in the UK and Ireland - "I weigh 11 stone 4" is completely normal there, and completely opaque everywhere else.
Definition: The SI base unit of mass - 1,000 grams.
History: For 130 years, the kilogram was defined by a single physical object: a golf-ball-sized cylinder of platinum and iridium nicknamed "Le Grand K," locked in a vault outside Paris and taken out for cleaning only once every 40 years. Every kilogram on Earth was, technically, defined by how much that one specific object weighed - which became a real problem once scientists discovered it had lost about 50 micrograms of mass over its lifetime, for reasons nobody could fully explain. In 2019, the kilogram was redefined using Planck's constant instead, a fundamental property of physics that can't drift, get scratched, or need cleaning.
Current use: The standard unit of mass in nearly every country on Earth, used in science, medicine, and everyday commerce.
The factor is 6.35029, which is derived rather than defined, so any decimal you see has been rounded somewhere.
For a quick estimate, multiply by 6. That is off by about 5.5%, which is fine for a rough figure and not fine for anything you are paying for or building to. Use the exact factor of 6.35029 when it matters.
The reverse factor is 0.158, so one kilogram is that many stone. Two decimal places is plenty for most purposes, and three is more than a tape measure can justify.
To anchor the scale: 1 stone is about 6.35 kg.