# 扭矩单位换算器（N·m、lb-ft）

> 为扭矩扳手和螺栓规格换算 N·m 与 lb-ft，以及 lb-in 和 kgf·m，使用精确关系 1 lbf·ft = 1.3558179483314004 N·m。

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

Torque is force times lever length, so every torque unit is a force unit multiplied by a length unit, held here as newton-metres. One pound-foot is 4.4482216152605 N × 0.3048 m = 1.3558179483314004 N·m exactly, a pound-inch is a twelfth of that, and a kilogram-force metre is 9.80665 N·m.

The default converts 100 N·m to 73.756 lbf·ft, the scale of wheel-nut and engine torque figures. Bicycle parts and small fasteners use smaller values: 5 N·m is 44.25 lbf·in.

Torque and energy share the dimension N·m, but NIST SP 811 specifies the newton metre, not the joule, as the unit of moment of force, so a torque is never written in joules.

## 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：newton-metre (N·m), kilonewton-metre (kN·m), pound-foot (lbf·ft), pound-inch (lbf·in), kilogram-force metre (kgf·m))
- **到** (选项：newton-metre (N·m), kilonewton-metre (kN·m), pound-foot (lbf·ft), pound-inch (lbf·in), kilogram-force metre (kgf·m))

## 结果

- 转换后的数值 — 主要结果
- 换算
- 换算系数
- 精确性

## 公式

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

## 计算示例

### 100 N·m in lbf·ft

- 数值: 100 N·m
- 从: newton-metre (N·m)
- 到: pound-foot (lbf·ft)
- **转换后的数值: 73.7562149277 lbf·ft**
- 核验来源：100 / (4.4482216152605 × 0.3048) (Python 3.8 fractions from the legal definitions)

### 1 lbf·ft in N·m

- 数值: 1 lbf·ft
- 从: pound-foot (lbf·ft)
- 到: newton-metre (N·m)
- **转换后的数值: 1.35581794833 N·m**
- **精确性: 精确**
- 核验来源：4.4482216152605 N × 0.3048 m = 1.3558179483314004 N·m (NIST SP 811 App. B)

### 12 lbf·in is 1 lbf·ft

- 数值: 12 lbf·in
- 从: pound-inch (lbf·in)
- 到: pound-foot (lbf·ft)
- **转换后的数值: 1 lbf·ft**
- 核验来源：12 in = 1 ft

### 1 kgf·m in N·m

- 数值: 1 kgf·m
- 从: kilogram-force metre (kgf·m)
- 到: newton-metre (N·m)
- **转换后的数值: 9.80665 N·m**
- 核验来源：9.80665 N × 1 m

## 常见问题

### How do I convert N·m to lb-ft?

Multiply by 0.737562, or divide by 1.35582. 100 N·m is 73.76 lbf·ft, and a 120 N·m wheel-nut setting is 88.51 lbf·ft. The factor comes from 1 lbf·ft = 4.4482216152605 N × 0.3048 m, which is exact, so only the reverse direction is rounded.

### Is lb-ft the same as ft-lb?

They are the same size, 1.3558 N·m. By convention the pound-foot (lb-ft, lbf·ft) is used for torque and the foot-pound (ft-lb, ft·lbf) for work or energy, mirroring the SI split between N·m for torque and joules for energy. In everyday use “ft-lb” is often written for torque too, and the number is the same.

### How do I convert lb-in to N·m?

Multiply by 0.112985. A pound-inch is one twelfth of a pound-foot, so 12 lbf·in = 1 lbf·ft = 1.3558 N·m. Small fasteners are specified in lbf·in or N·m: 50 lbf·in is 5.65 N·m, and 5 N·m is 44.25 lbf·in.

### What is a kgf·m in N·m?

Exactly 9.80665 N·m, the torque of one kilogram-force on a 1 m lever. Older workshop manuals give torque in kgf·m, sometimes written kg·m or kgm, so a 10 kgf·m figure is 98.07 N·m or 72.33 lbf·ft.

### Why is torque not measured in joules?

Torque and energy are different quantities that happen to share the dimension N·m. NIST SP 811 states that the SI unit of moment of force is the newton metre rather than the joule. Energy is force times distance moved, torque is force times lever arm, and a torque of 1 N·m acting through one full turn does 2π J of work.

### “扭矩单位换算器（N·m、lb-ft）”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，“100 N·m in lbf·ft”根据100 / (4.4482216152605 × 0.3048) (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)