Pound-force under standard gravity.
Pound-forces to Kilogram-forces Converter — lbf to kgf
Convert Pound-force (lbf) to Kilogram-force (kgf) using the exact conversion factor (1 pound-force = 0.45359237 kilogram-force). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Pound-forces to Kilogram-forces converter
Converter
Force Converter
Convert newtons, dynes, pound-force, kilogram-force, kips, and ounce-force.
Context values
Some unit families need one extra value for a physically accurate result.
Kilogram-force under standard gravity.
Result = input x 4.448221615 / 9.80665.
Force uses the newton as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Pound-forces to Kilogram-forces
Pound-force and Kilogram-force both measure force, and the conversion matters whenever an SI-trained engineer needs to compare notes with a US-trained one, or vice versa. Pound-force is typically associated with united States (engineering, aerospace), while Kilogram-force is typically associated with still encountered in some older European and Asian engineering specifications and torque-related equipment, though official use has been phased out in favor of the newton.
Formula
kilogram-forces = pound-forces × 0.45359237
This factor comes from each unit's defined relationship to the category's base unit: 1 pound-force equals 4.44822161526 base units, and 1 kilogram-force equals 9.80665 base units, so dividing one by the other gives the direct pound-force-to-kilogram-force factor of 0.45359237.
Simple example
1 lbf × 0.45359237 = 0.45359237 kgf
1 pound-force = 0.45359237 kilogram-forces.
Real-world example
10 lbf × 0.45359237 = 4.5359237 kgf
10 pound-forces = 4.5359237 kilogram-forces.
Conversion table
| Pound-force (lbf) | Kilogram-force (kgf) |
|---|---|
| 1 lbf | 0.45359237 kgf |
| 5 lbf | 2.26796185 kgf |
| 10 lbf | 4.5359237 kgf |
| 50 lbf | 22.6796185 kgf |
| 100 lbf | 45.359237 kgf |
| 1,000 lbf | 453.59237 kgf |
Reverse conversion: Kilogram-force to Pound-force
0.45359237 kgf × 2.204622622 = 1 lbf
0.45359237 kilogram-forces = 1 pound-force.
pound-forces = kilogram-forces × 2.20462262185
For a page dedicated to this direction, see Kilogram-force to Pound-force.
Pound-force vs. Kilogram-force
| Aspect | Pound-force | Kilogram-force |
|---|---|---|
| Family | US/imperial customary unit | non-SI unit, deprecated but still encountered |
| Typical use | US engineering and aerospace force specifications | Appears on some older or legacy engineering and mechanical specifications, particularly torque wrenches and spring-force ratings, predating wider adoption of the newton |
| Where it's used | United States (engineering, aerospace) | Still encountered in some older European and Asian engineering specifications and torque-related equipment, though official use has been phased out in favor of the newton |
Understanding the Pound-force
Pound-force (lbf) measures force. A pound-force is the force exerted by standard gravity on one pound-mass: exactly 4.4482216152605 newtons. It is classified as a US/imperial customary unit.
Where it's used: United States (engineering, aerospace)
Pound-force vs. pound-mass. Pound-force (lbf) measures force, while the plain 'pound' almost always refers to pound-mass; the two are related by standard gravity, not identical — a common source of confusion in US engineering units.
Uses of the Pound-force today
- US engineering and aerospace force specifications
- Torque and pressure units derived from it (psi, foot-pounds)
- Automotive and mechanical specifications
History of the Pound-force
Pound-force was defined to let US engineers keep using the familiar pound in force calculations, fixed via standard gravity (9.80665 m/s²) acting on one pound-mass, once the pound-mass itself was standardized in 1959.
Historical origin. Pound-force was not the invention of a single named person; it developed through the process described above.
Understanding the Kilogram-force
Kilogram-force (kgf) measures force. Defined as the force exerted by standard gravity on a mass of one kilogram — exactly 9.80665 newtons. It is classified as a non-SI unit, deprecated but still encountered.
Where it's used: Still encountered in some older European and Asian engineering specifications and torque-related equipment, though official use has been phased out in favor of the newton
Kilogram-force vs. newton. The newton is the modern SI unit of force; kilogram-force is an older, gravity-dependent unit still occasionally seen on legacy equipment. 1 kgf equals exactly 9.80665 N.
Uses of the Kilogram-force today
- Appears on some older or legacy engineering and mechanical specifications, particularly torque wrenches and spring-force ratings, predating wider adoption of the newton
Pound-force — sources
- NIST Special Publication 811 — Documents the pound-force definition via standard gravity.
Kilogram-force — sources
- BIPM SI Brochure — Notes kilogram-force among non-SI force units whose use is discouraged in favor of the newton.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilogram-forces are in 1 pound-force?
1 pound-force equals 0.45359237 kilogram-forces, using the exact defined conversion factor rather than an estimate.
How do I convert pound-force to kilogram-force?
Multiply the pound-force value by 0.45359237. The converter above does this instantly to whatever precision you set.
How do I convert kilogram-force back to pound-force?
Use the reverse factor: 1 kilogram-force equals 2.204622622 pound-forces. You can also use the swap control in the converter above to flip the direction instantly.
What is a pound-force?
Pound-force (lbf) measures force. A pound-force is the force exerted by standard gravity on one pound-mass: exactly 4.4482216152605 newtons. It is classified as a US/imperial customary unit.
What is a kilogram-force?
Kilogram-force (kgf) measures force. Defined as the force exerted by standard gravity on a mass of one kilogram — exactly 9.80665 newtons. It is classified as a non-SI unit, deprecated but still encountered.
Is the pound-force to kilogram-force conversion exact?
Yes. Defined as the force exerted by standard gravity on a mass of one kilogram — exactly 9.80665 newtons. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between pound-force vs. pound-mass?
Pound-force (lbf) measures force, while the plain 'pound' almost always refers to pound-mass; the two are related by standard gravity, not identical — a common source of confusion in US engineering units.
Where is the pound-force still used today?
United States (engineering, aerospace)