# トルク換算（N·m、lb-ft）

> トルクレンチやボルトの仕様に合わせ、N·m と lb-ft、lb-in、kgf·m を換算します。正確な関係 1 lbf·ft = 1.3558179483314004 N·m を使います。

操作できるページ：https://www.calcopenly.com/ja/conversion/torque-converter
分野：単位換算ツール

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.

## 入力

- **値**: 変換元の単位で数値を入力するか、単位付きの数値を入力します
- **変換元** (選択肢：newton-metre (N·m), kilonewton-metre (kN·m), pound-foot (lbf·ft), pound-inch (lbf·in), kilogram-force metre (kgf·m))
- **変換先** (選択肢：newton-metre (N·m), kilonewton-metre (kN·m), pound-foot (lbf·ft), pound-inch (lbf·in), kilogram-force metre (kgf·m))

## 結果

- 変換後の値 — 主な結果
- 単位換算
- 換算係数
- 正確さ

## 計算式

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

## 計算例

### 100 N·m in lbf·ft

- 値: 100 N·m
- 変換元: newton-metre (N·m)
- 変換先: pound-foot (lbf·ft)
- **変換後の値: 73.7562149277 lbf·ft**
- 照合元：100 / (4.4482216152605 × 0.3048) (Python 3.8 fractions from the legal definitions)

### 1 lbf·ft in N·m

- 値: 1 lbf·ft
- 変換元: pound-foot (lbf·ft)
- 変換先: newton-metre (N·m)
- **変換後の値: 1.35581794833 N·m**
- **正確さ: 正確**
- 照合元：4.4482216152605 N × 0.3048 m = 1.3558179483314004 N·m (NIST SP 811 App. B)

### 12 lbf·in is 1 lbf·ft

- 値: 12 lbf·in
- 変換元: pound-inch (lbf·in)
- 変換先: pound-foot (lbf·ft)
- **変換後の値: 1 lbf·ft**
- 照合元：12 in = 1 ft

### 1 kgf·m in N·m

- 値: 1 kgf·m
- 変換元: kilogram-force metre (kgf·m)
- 変換先: newton-metre (N·m)
- **変換後の値: 9.80665 N·m**
- 照合元：9.80665 N × 1 m

## よくある質問

### 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.

### 「トルク換算（N·m、lb-ft）」の精度はどのくらいですか？

精度は入力値と計算方法の前提に依存します。十進演算には有効数字50桁を使いますが、推定、数値計算手法、元データの精度はそれより低い場合があります。表示の丸め処理でこれらの制約がなくなるわけではありません。 独立した出典の解答と照合した計算例：4。 例えば、「100 N·m in lbf·ft」は100 / (4.4482216152605 × 0.3048) (Python 3.8 fractions from the legal definitions)と照合しています。

### この計算方法の出典は何ですか？

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.

## 出典

- [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)