Free online force converter. Convert newtons (N) to pounds-force (lbf), kilograms-force (kgf), dynes, and poundals instantly — for physics, engineering, and mechanics. Accurate, instant, no sign-up.
newton • lbf • kgf • dyne • poundal
Convert between newtons and pounds-force for homework, lab reports, and understanding F = ma calculations.
Structural loads, spring forces, and actuator ratings switch between SI (N, kN) and US (lbf) units.
Rocket thrust, winch capacity, and tensile strength are quoted in different force units worldwide.
Force is measured in newtons (N) in the SI system, defined as the force needed to accelerate 1 kilogram at 1 meter per second squared (F = ma). The most common US conversion is to pounds-force (lbf): 1 lbf = 4.44822 newtons, and 1 N = 0.224809 lbf. Pounds-force represents the gravitational force on a one-pound mass at Earth's surface, which is why it's intuitive for weight-based engineering in the US. A 100 lbf load equals 444.8 N.
Kilograms-force (kgf, also called kilopond) is the force of gravity on a 1 kg mass: 1 kgf = 9.80665 N = 2.20462 lbf. It appears in older European specs and some everyday contexts (like bicycle spoke tension). The dyne is the tiny CGS unit (1 N = 100,000 dynes) used in physics, while the poundal is an older imperial unit (1 poundal = 0.138 N). Understanding force conversions is essential for physics coursework, structural and mechanical engineering, comparing international equipment ratings, and any work involving thrust, tension, or load.
1 lbf = 4.448 N. 10 lbf = 44.5 N. 50 lbf = 222.4 N. 100 lbf = 444.8 N. 1 kgf = 9.807 N = 2.205 lbf. 1 kN = 224.8 lbf.
Holding an apple: ~1 N. Body weight (70 kg person): ~686 N = 154 lbf. Car braking: ~5,000 N. The number 1 N ≈ the weight of a small apple.
Rocket engine thrust: millions of N. Elevator cable: ~50 kN. Bolt clamping force: 10–100 kN. Bridge cable tension: thousands of kN.
Mass (kg) is constant; weight (force, in N) depends on gravity. A 1 kg mass weighs 9.81 N on Earth but only 1.62 N on the Moon. Don't confuse them.
Force and mass are distinct quantities that imperial units habitually blur. The newton is defined from Newton's second law as the force accelerating one kilogram at one metre per second squared, so it is built from base units. The pound-force, by contrast, is the weight of one pound of mass in standard gravity — which embeds the value 9.80665 m/s² into the definition and means the same mass has a different weight on the Moon while its mass is unchanged. The kilogram-force, still seen on older European equipment, has the same problem.
newtons = value × factor_fromresult = N ÷ factor_toF = m × a · 1 lbf = 4.4482216 N · 1 kgf = 9.80665 Nwhere:
Assumptions: Standard gravity is a defined constant; real local gravity varies by about 0.5% between the equator and the poles, which matters for precision weighing and not for engineering loads.
SourceBIPM SI Brochure
A fastener rated at 150 pound-force converted for a specification written in SI.
Result150 lbf = 667.23 N = 68.04 kgf
The numerical coincidence between pounds of mass and pound-force under earth gravity is why the distinction is so easily lost. It reappears immediately in dynamics: a 150 lb mass decelerating in a crash exerts many times 150 lbf.