What this calculator does
The pound-force is a unit of force, used mostly in older engineering and imperial-unit specifications for things like spring tension, torque wrenches and towing capacity. The newton is the SI unit of force. Converting between them is a fixed multiplication, since both units are defined constants rather than anything that changes with location or measurement conditions.
It is easy to confuse this with converting a mass in pounds to kilograms, but that is a different physical quantity entirely. Pound-force already measures a force (weight under standard gravity), so it converts directly to newtons with a single multiplier. A pound of mass has to first be multiplied by gravitational acceleration before it becomes a force in newtons.
The formula
Multiply the pound-force value by 4.4482216152605 to get newtons. To go the other way, divide the newton value by the same factor. This factor is the internationally defined equivalence between the two units and does not change.
| Term | Meaning |
|---|---|
| lbf | Pound-force: the imperial unit of force, historically defined as the weight of one pound-mass under standard gravity. |
| N | Newton: the SI unit of force, defined as the force needed to accelerate one kilogram at one metre per second squared. |
| Conversion factor | 4.4482216152605, the fixed number of newtons in one pound-force. |
The inputs explained
| Field | What to enter |
|---|---|
| Value to convert | The number to convert, in whichever unit you are starting from. |
| Direction | Choose whether you are converting pounds-force into newtons, or newtons back into pounds-force. |
When to use it
Reading an imperial torque wrench spec
Some torque and force specifications from older or US-sourced equipment manuals are given in pound-force, either alone or as part of a foot-pounds figure, and need converting to newtons to match metric documentation.
Comparing spring or load ratings
Spring tension, tow-bar capacity and load-cell ratings are sometimes quoted in lbf on imported parts. Converting to newtons lets you compare them directly against a metric-rated component.
Checking a physics or engineering calculation
Where a formula expects force in newtons but a source value is given in pound-force, converting first avoids an error that would carry through the rest of the working.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many newtons is a given pound-force value?
Common pound-force values converted to newtons using the fixed factor.
| Pounds-force (lbf) | Newtons |
|---|---|
| 1 lbf | 4.448 N |
| 5 lbf | 22.241 N |
| 10 lbf | 44.482 N |
| 50 lbf | 222.411 N |
| 100 lbf | 444.822 N |
| 500 lbf | 2,224.111 N |
How many pounds-force is a given newton value?
Common newton values converted back to pounds-force.
| Newtons (N) | Pounds-force |
|---|---|
| 1 N | 0.2248 lbf |
| 10 N | 2.248 lbf |
| 50 N | 11.240 lbf |
| 100 N | 22.481 lbf |
| 500 N | 112.404 lbf |
| 1000 N | 224.809 lbf |
Questions
Is pound-force the same as pound (mass)?
No. Pound-force measures force, while pound (or pound-mass) measures mass. They are numerically related through gravity but are different physical quantities, and converting mass in pounds to kilograms uses a completely different factor to this one.
Why is the conversion factor 4.4482216152605 and not a rounder number?
The pound-force is defined from the international avoirdupois pound (exactly 0.45359237 kg) multiplied by standard gravity (9.80665 m/s squared), and that multiplication does not land on a round figure.
Where does pound-force still get used?
Mainly in older imperial engineering specifications, some US industrial and aerospace documentation, and imported hardware such as torque wrenches, tow hitches and load cells rated in lbf.
Can I use this for torque instead of force?
No, torque combines force with a distance, such as foot-pounds or newton-metres. Use a dedicated torque converter for that; this tool handles force alone.
For torque units such as foot-pounds and newton-metres, see the torque converter. To convert a mass in kilograms to its weight force in newtons, see the kg to newtons converter.