# 重量换算器（kg、lb、英石、oz）

> 按1959年磅的精确定义换算kg与磅、英石到kg、盎司到克，也支持吨、克拉、金衡盎司和托拉。

交互版本：https://www.calcopenly.com/zh/conversion/weight-converter
主题：单位换算器

Every mass unit is a fixed number of kilograms. The pound has been exactly 0.45359237 kg since the 1959 international yard and pound agreement, so pounds, ounces (1/16 lb), stones (14 lb) and short and long tons all convert exactly. The kilogram itself has been defined since 2019 by a fixed value of the Planck constant.

The default converts 1 kg to 2.20462262185 lb, a repeating decimal shown to 12 significant figures. Body weight is the usual reason to convert: 70 kg is 154.32 lb, or just over 11 stone.

Weight here means mass, the sense in which scales and shops use the word. Precious metals use the troy ounce (31.1034768 g) rather than the ordinary ounce (28.349523125 g), and gems are weighed in metric carats of exactly 200 mg.

## 输入

- **数值**: 输入源单位下的数值，也可以输入带有自身单位的数值
- **从** (选项：kilogram (kg), gram (g), milligram (mg), microgram (µg), tonne (t), quintal (q), pound (lb), ounce (oz), stone (st), short ton (ton (US)), long ton (ton (UK)), carat (ct), grain (gr), troy ounce (oz t), tola)
- **到** (选项：kilogram (kg), gram (g), milligram (mg), microgram (µg), tonne (t), quintal (q), pound (lb), ounce (oz), stone (st), short ton (ton (US)), long ton (ton (UK)), carat (ct), grain (gr), troy ounce (oz t), tola)

## 结果

- 转换后的数值 — 主要结果
- 换算
- 换算系数
- 精确性

## 公式

$$
\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{kg} \end{gathered}
$$

## 计算示例

### 1 kg to pounds

- 数值: 1 kg
- 从: kilogram (kg)
- 到: pound (lb)
- **转换后的数值: 2.2046226218 lb**
- **精确性: 定义精确，结果为循环小数**
- 核验来源：1 lb = 0.45359237 kg exactly (1959 agreement); 1/0.45359237 = 100000000/45359237 (Python 3.8 fractions from the legal definitions)

### 1 stone in pounds

- 数值: 1 st
- 从: stone (st)
- 到: pound (lb)
- **转换后的数值: 14 lb**
- 核验来源：NIST HB 44 App. C: 1 stone = 14 lb

### 1 ounce in grams

- 数值: 1 oz
- 从: ounce (oz)
- 到: gram (g)
- **转换后的数值: 28.349523125 g**
- **精确性: 精确**
- 核验来源：1/16 × 453.59237 g = 28.349523125 g (NIST HB 44 App. C)

### 1 tola in grams

- 数值: 1 tola
- 从: tola
- 到: gram (g)
- **转换后的数值: 11.6638038 g**
- 核验来源：1 tola = 180 grains; 1 grain = 64.79891 mg exactly (NIST HB 44 App. C): 180 × 64.79891 mg

## 常见问题

### How many pounds are in a kilogram?

2.20462262 lb. The pound is defined as exactly 0.45359237 kg, so 1 kg = 1 ÷ 0.45359237 = 2.2046226218… lb, a decimal that never ends. The shortcut “multiply by 2.2” is 0.2% low: 100 kg is 220.46 lb, not 220.

### How many kilograms are in a stone?

Exactly 6.35029318 kg. A stone is 14 lb, and 14 × 0.45359237 kg gives that figure. Stones are still used for body weight in the UK and Ireland; 11 st 7 lb is 161 lb, which is 73.03 kg.

### What is the difference between a troy ounce and an ounce?

A troy ounce is 31.1034768 g and an ordinary (avoirdupois) ounce is 28.349523125 g, so the troy ounce is 9.7% heavier. Gold, silver and platinum prices are quoted per troy ounce. A troy pound has 12 troy ounces, while the ordinary pound has 16 ounces.

### Is a ton the same as a tonne?

No. A tonne (metric ton) is 1,000 kg. A US short ton is 2,000 lb, 907.18474 kg, and a UK long ton is 2,240 lb, 1,016.0469088 kg. The long ton is 12% heavier than the short ton, so shipping and freight documents should state which one they use.

### How many grams is a tola?

11.6638038 g. A tola is 180 grains, and a grain is exactly 64.79891 mg (NIST Handbook 44), so 180 × 64.79891 mg = 11.6638038 g. Gold is still traded by the tola in South Asia and the Gulf, where a 10-tola bar weighs 116.64 g.

### “重量换算器（kg、lb、英石、oz）”有多准确？

准确性取决于输入值和方法的假设。十进制运算使用50位有效数字，但估算、数值方法和源数据的精度可能较低；显示时的舍入并不能消除这些限制。 已按独立来源核验的计算示例：4。 例如，“1 kg to pounds”根据1 lb = 0.45359237 kg exactly (1959 agreement); 1/0.45359237 = 100000000/45359237 (Python 3.8 fractions from the legal definitions)进行核验。

### 这种方法出自哪里？

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement.

## 来源

- [NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C — General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)