# Convertisseur de force

> Convert kgf to newtons, lbf to N and kN to kgf or lbf, using standard gravity (9.80665 m/s²) and the exact pound-force of 4.4482216152605 N.

Version interactive : https://www.calcopenly.com/fr/conversion/force-converter
Sujet : Convertisseurs d’unités

Every force unit is a fixed number of newtons, and one newton accelerates 1 kg at 1 m/s². The gravitational units use standard gravity, g₀ = 9.80665 m/s², set by the 3rd CGPM in 1901: a kilogram-force is 9.80665 N and a pound-force is 0.45359237 kg × 9.80665 m/s² = 4.4482216152605 N, both exact.

The default converts 1 kgf to 9.80665 N. Loads marked in kilograms-force or tonnes-force and climbing or lifting gear rated in kilonewtons are the usual reasons to convert: 1 kN is 101.97 kgf or 224.81 lbf.

A kilogram is a mass and a newton a force, so “1 kg = 9.81 N” holds only under standard gravity. Real gravity runs from about 9.78 m/s² at the equator to 9.83 m/s² at the poles, a spread of 0.5%.

## Données

- **Valeur**: Un nombre dans l’unité de départ, ou accompagné de sa propre unité
- **De** (options : newton (N), kilonewton (kN), dyne (dyn), pound-force (lbf), kilogram-force (kgf), ounce-force (ozf), poundal (pdl))
- **Vers** (options : newton (N), kilonewton (kN), dyne (dyn), pound-force (lbf), kilogram-force (kgf), ounce-force (ozf), poundal (pdl))

## Résultats

- Valeur convertie — résultat principal
- Conversion
- Facteur de conversion
- Exactitude

## Formule

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

## Exemples détaillés

### 1 kgf in newtons

- Valeur: 1 kgf
- De: kilogram-force (kgf)
- Vers: newton (N)
- **Valeur convertie: 9.80665 N**
- Source de vérification : 1 kgf = 1 kg × 9.80665 m/s² (standard gravity, CGPM 1901)

### 1 lbf in newtons

- Valeur: 1 lbf
- De: pound-force (lbf)
- Vers: newton (N)
- **Valeur convertie: 4.44822161526 N**
- **Exactitude: Exact**
- Source de vérification : 0.45359237 kg × 9.80665 m/s² = 4.4482216152605 N (NIST SP 811 App. B)

### 1 kN in lbf

- Valeur: 1 kN
- De: kilonewton (kN)
- Vers: pound-force (lbf)
- **Valeur convertie: 224.8089431 lbf**
- Source de vérification : 1000 / 4.4482216152605 (Python 3.8 fractions from the legal definitions)

### 1 N in dynes

- Valeur: 1 N
- De: newton (N)
- Vers: dyne (dyn)
- **Valeur convertie: 100,000 dyn**
- Source de vérification : 1 dyn = 10⁻⁵ N (NIST SP 811 App. B)

## Questions

### How many newtons are in a kilogram?

A mass of 1 kg weighs 9.80665 N under standard gravity, which is the definition of 1 kilogram-force. The kilogram measures mass and the newton force, so the conversion needs an acceleration; 9.80665 m/s² is the conventional value fixed in 1901, and local gravity differs from it by up to about 0.3%.

### How do I convert lbf to newtons?

Multiply by 4.4482216152605, usually rounded to 4.448. One pound-force is the weight of one pound (0.45359237 kg) under standard gravity, so the factor is exact. A 200 lbf load is 889.64 N, and 1 N is 0.224809 lbf.

### How many kgf is 1 kN?

101.97 kgf. Multiply kilonewtons by 101.9716, or divide by 0.00980665, to get kilograms-force. A carabiner marked 22 kN is rated to 2,243 kgf, or 4,946 lbf, and a 5 kN anchor to 510 kgf. The factor is exact because the kilogram-force is defined with standard gravity, 9.80665 m/s².

### What is the difference between a pound and a pound-force?

A pound (lb) is mass, 0.45359237 kg; a pound-force (lbf) is the weight of that mass under standard gravity, 4.4482216152605 N. On Earth a 10 lb object weighs about 10 lbf, which is why everyday speech uses one word for both. The poundal, 0.138255 N, is the force that accelerates 1 lb at 1 ft/s².

### How many newtons does a person weigh?

A 70 kg person weighs 686.47 N under standard gravity (70 × 9.80665), which is 70 kgf or 154.3 lbf. Bathroom scales measure this force and divide by g to display kilograms, so a scale set up for standard gravity reads about 0.3% low at the equator and 0.3% high at the poles.

### Quelle est la précision de « Convertisseur de force » ?

La précision dépend de vos données et des hypothèses de la méthode. Le calcul décimal utilise 50 chiffres significatifs, mais les estimations, méthodes numériques et données sources peuvent être moins précises ; l’arrondi affiché ne supprime pas ces limites. Exemples résolus vérifiés à partir de sources indépendantes : 4. Par exemple, « 1 kgf in newtons » est vérifié à l’aide de 1 kgf = 1 kg × 9.80665 m/s² (standard gravity, CGPM 1901).

### D’où vient cette méthode ?

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.

## Sources

- [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)