The exact factor, and a shortcut
One pound-force is defined as 0.45359237 kg × 9.80665 m/s², which is exactly 4.4482216152605 N. For a fast estimate, multiply pounds by 4.45 (or by 4.5 if you only need a ballpark). Going the other way, divide newtons by about 4.45.
Quick reference
| Pound-force | Newtons | Roughly |
|---|---|---|
| 1 lbf | 4.45 N | the conversion factor |
| 10 lbf | 44.5 N | a full grocery bag (~4.5 kg) |
| 50 lbf | 222.4 N | an average hand grip |
| 100 lbf | 444.8 N | firm assembly pressure |
| 150 lbf | 667.2 N | a 150 lb person's weight |
| 1,000 lbf | 4,448 N | a structural load |
| 10,000 lbf | 44,482 N | a car's braking force |
Engine thrust is usually quoted in kilonewtons (1 kN = 1,000 N). A single F-16 engine puts out about 28,600 lbf, or 127 kN.
Pound-force is a force, pound-mass is a mass
The trap in this conversion is that "pounds" can mean two different things. A newton and a pound-force both measure force; a pound-mass (like a kilogram) measures the amount of matter. They only line up on Earth.
The same one-pound mass weighs a sixth as much on the Moon. Its mass never changes; only the force gravity exerts on it does — which is exactly what a newton or pound-force measures.
Two details that trip people up
- Use 9.80665, not 9.81. Standard gravity is defined exactly as 9.80665 m/s². Rounding to 9.81 shifts the answer by about 0.03%.
- Watch kN vs N. Thrust and large structural loads are given in kilonewtons. A "127" next to a jet engine means 127 kN, which is 127,000 N.
Common questions
How many newtons are in one pound-force?
1 lbf equals 4.44822 newtons (exactly 4.4482216152605 N). It comes from one avoirdupois pound of mass, 0.45359237 kg, times standard gravity, 9.80665 metres per second squared.
How do I convert pounds to newtons?
Multiply the pound-force value by 4.44822. So 50 lbf is 222.4 N. For a quick mental estimate, multiply by 4.45; the error is under a tenth of a percent.
Is pound-force the same as a pound of weight?
Numerically, yes, at Earth's surface. A pound-force is the weight of one pound of mass under standard gravity. The distinction only bites when gravity changes: one pound of mass weighs about 0.17 lbf on the Moon.
How many newtons is my body weight?
Multiply your weight in pounds by 4.45. A 150-pound person weighs about 667 N; a 200-pound person, about 890 N.
