To convert pounds to stone (lb to st), multiply by 0.071429. 1 pound equals 0.071429 st, about the same as a loaf of sandwich bread.
| pounds | stone |
|---|---|
| 1 pound | 0.071429 st |
| 2 pounds | 0.14286 st |
| 5 pounds | 0.35714 st |
| 10 pounds | 0.71429 st |
| 25 pounds | 1.7857143 st |
| 50 pounds | 3.5714286 st |
| 100 pounds | 7.1428571 st |
| 250 pounds | 17.857143 st |
| 500 pounds | 35.714286 st |
| 1000 pounds | 71.428571 st |
Definition: Exactly 0.45359237 kilograms - 16 ounces.
History: The pound descends from the Roman "libra," which is also where the abbreviation "lb" comes from - it never matched the English word at all. It went through numerous competing regional definitions over the centuries until the "avoirdupois" pound was standardized, then finally locked to an exact metric value in 1959 by international agreement - meaning the pound has been officially defined in terms of the kilogram, not the other way around, for over 60 years.
Current use: Everyday weight in the US, including body weight, food packaging, and shipping. The UK largely moved to metric but still uses pounds, and stone, for body weight specifically.
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.
The factor is 0.0714286, which is derived rather than defined, so any decimal you see has been rounded somewhere.
No simple round multiplier is close enough to be useful, so this is one to look up rather than estimate. The exact factor is 0.0714286.
Going the other way, one stone is 14 lb, which is usually the easier direction to work in. Because the forward factor is small, watch the decimal place rather than the digits: a factor-of-ten slip is the common error, not a rounding one.
To anchor the scale: 20 pounds is about 1.43 st.