Force Converter

Q: What is the difference between lb and lbf?

The pound lb is a mass, 0.45359237 kg. The pound force lbf is the weight of that mass under standard gravity, 4.4482216152605 N.

Force Converter

Convert force between newtons, kilonewtons, kilogram-force, pound-force, kips, dynes and poundals with exact definitions and the formula.

Value

From

–

Formula:

Significant figures

≈ means the result was rounded to the chosen number of significant figures.

Kilogram-force and pound-force are defined with standard gravity gₙ = 9.80665 m/s²: 1 kgf = 9.80665 N and 1 lbf = 4.4482216152605 N, exactly.

{value} in every unit

Unit	Result

Quick conversion table: {from} to {to}

From	To

Common values

Reference	Value	Result

Unit definitions

Unit

How to use the force converter

Type a force in Value. A decimal point or a decimal comma both work.
Choose the starting unit in From and the target unit in To, for example newton and pound-force.
The result appears as you type, with the complete line below it (“100 N ≈ 22.480894 lbf”). Copy copies that line.
Swap units (⇄) reverses the conversion.
Significant figures controls the rounding; “≈” marks a rounded value.

You also get the force in every unit, a quick table for the selected pair, a few references (the weight of an apple, of 1 kg, of an adult, the thrust of an airliner engine) and each unit expressed in newtons.

The units and their definitions

Newton (N): the SI unit of force, the force that accelerates 1 kg by 1 m/s². 1 kN = 1,000 N.
Dyne (dyn): the CGS unit, 1 g·cm/s² = 10⁻⁵ N. It survives in physics, for example in surface tension (dyn/cm).
Kilogram-force (kgf): the weight of 1 kg under standard gravity gₙ = 9.80665 m/s², a value adopted by the 3rd General Conference on Weights and Measures in 1901. So 1 kgf = 9.80665 N exactly, and 1 gram-force (gf) = 0.00980665 N. You may also see it written kp (kilopond).
Pound-force (lbf): the weight of one avoirdupois pound (0.45359237 kg) under the same standard gravity. 1 lbf = 4.4482216152605 N exactly.
Kip: 1,000 lbf, about 4.448 kN, used in US structural engineering.
Poundal (pdl): the force that accelerates 1 lb by 1 ft/s², 0.138254954376 N. It is the imperial counterpart of the newton, now rare.

Since both gravitational units use the same gₙ, 1 lbf = 0.45359237 kgf, exactly the ratio between the pound and the kilogram.

Mass or force?

In everyday language, “weight” in kilograms is a mass. In physics, weight is a force: mass × gravitational acceleration. A 70 kg person has a weight of about 686 N on Earth, which is 70 kgf only at standard gravity. Real gravity varies from about 9.78 m/s² at the equator to 9.83 m/s² at the poles, so the same mass does not produce quite the same force everywhere, and on the Moon it would be about six times smaller.

The kilogram-force and pound-force are therefore convenient but slightly misleading: they are forces, defined with a fixed conventional gravity, not with the local one.

Quick equivalents

1 N ≈ 0.10197 kgf ≈ 0.22481 lbf
1 kgf = 9.80665 N ≈ 2.20462 lbf
1 lbf ≈ 4.44822 N ≈ 0.45359 kgf
1 kN ≈ 101.97 kgf ≈ 224.81 lbf

Frequently asked questions

How do I convert newtons to kilograms?

Strictly, you can’t: newtons measure force and kilograms mass. But under standard gravity a force of 1 N is the weight of about 0.102 kg, so divide by 9.80665 to get kilogram-force.

How many newtons is 1 kg?

The weight of a 1 kg mass under standard gravity is 1 kgf = 9.80665 N. For quick estimates, 10 N per kilogram is within 2 %.

What is the difference between lb and lbf?

The pound (lb) is a mass, 0.45359237 kg. The pound-force (lbf) is the weight of that mass under standard gravity, 4.4482216152605 N.

Why do climbing ropes and anchors use kN?

Because the peak forces in a fall are large and short. A carabiner rated 24 kN holds about 2,447 kgf, or roughly 5,395 lbf.

Can I enter a negative force?

Yes. A negative value, such as a force in the opposite direction, converts with the same factor.