How this conversion works
Force is mass times acceleration. The SI unit, the newton, is the force that accelerates 1 kg at 1 m/s².
Gravitational units such as the pound-force and kilogram-force are the weight of a reference mass under standard gravity (9.80665 m/s², exact). One pound-force is therefore 0.45359237 kg × 9.80665 m/s² = 4.4482216152605 N.
Formula: result = value × (base units per source unit) ÷ (base units per target unit)
Where this conversion is used
- Load ratings on hoists, straps and anchors given in kN, kgf or lbf.
- Structural loads in kips and kilonewtons.
- Spring, actuator and load-cell specifications.
- Physics homework moving between SI and US units.
Worked example: 100 N to pound-force
- One lbf = 4.4482216152605 N.
- 100 ÷ 4.4482216152605 = 22.4809 lbf.
Unit definitions
| Unit | In newtons | Note |
|---|---|---|
| Newton (N) | 1 | SI unit: 1 kg·m/s². |
| Kilonewton (kN) | 1,000 | |
| Meganewton (MN) | 1,000,000 | |
| Dyne (dyn) | 0.00001 | CGS unit: 1 g·cm/s² = 10⁻⁵ N exactly. |
| Pound-force (lbf) | 4.4482216153 | 0.45359237 kg × 9.80665 m/s² = 4.4482216152605 N. |
| Ounce-force (ozf) | 0.278013851 | |
| Kip (kilopound-force) (kip) | 4,448.22161526 | |
| Kilogram-force (kgf) | 9.80665 | 9.80665 N exactly (standard gravity). |
| Gram-force (gf) | 0.00980665 | |
| Ton-force (short) (tonf (US)) | 8,896.44323052 | |
| Poundal (pdl) | 0.1382549544 | 1 lb·ft/s² = 0.138254954376 N exactly. |
Newtons to pounds-force
| Newton (N) | Pound-force (lbf) |
|---|---|
| 1 | 0.2248 |
| 5 | 1.124 |
| 10 | 2.2481 |
| 50 | 11.2404 |
| 100 | 22.4809 |
| 500 | 112.4045 |
| 1,000 | 224.8089 |
Pounds-force to newtons
| Pound-force (lbf) | Newton (N) |
|---|---|
| 1 | 4.4482 |
| 5 | 22.2411 |
| 10 | 44.4822 |
| 25 | 111.2055 |
| 50 | 222.4111 |
| 100 | 444.8222 |
| 1,000 | 4,448.2216 |
Things to watch for
- A kilogram-force is not a mass. A 1 kg object weighs about 1 kgf only where gravity is close to standard gravity.
Precision and sources
Results are calculated from the definitions above and rounded to 12 significant digits; the converter shows up to eight decimal places and the tables four. Reference: NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B.
Frequently asked questions
Is a pound the same as a pound-force?
No. The pound (lb) is a mass; the pound-force (lbf) is the weight of one pound under standard gravity. In everyday US usage both are often written “pounds.”
What is a kip?
A kip is 1,000 pound-force (about 4,448 N). It is common in US structural engineering for loads on beams and columns.