Newton to Kilogram-force
N
kgf
Conversion History
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|---|---|---|
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Quick Reference Table (Newton to Kilogram-force)
| Newton (N) | Kilogram-force (kgf) |
|---|---|
| 1 | 0.10197162129779999902 |
| 10 | 1.01971621297799999023 |
| 50 | 5.09858106488999995115 |
| 100 | 10.1971621297799999023 |
| 500 | 50.98581064889999951149 |
| 1,000 | 101.97162129779999902298 |
| 9,806.65 | 1,000.0000000000703604187 |
About Newton (N)
The newton (N) is the SI unit of force, defined as the force required to accelerate a mass of one kilogram at one meter per second squared. It is the standard unit across physics and engineering worldwide. One newton is approximately the force exerted by gravity on a 102-gram object at Earth's surface — roughly the weight of a medium apple. Structural engineering uses kilonewtons (kN); propulsion engineering uses meganewtons (MN). The newton appears in every derived SI unit involving force: pressure (Pa = N/m²), energy (J = N·m), and power (W = N·m/s).
The weight of a 1 kg mass at Earth's surface is about 9.81 N. A firm handshake exerts roughly 100–150 N.
Etymology: Named after Sir Isaac Newton (1643–1727), English mathematician and physicist who formulated the three laws of motion and the law of universal gravitation in Principia Mathematica (1687). The unit was adopted by the General Conference on Weights and Measures in 1948.
About Kilogram-force (kgf)
The kilogram-force (kgf), also called kilopond (kp), is the gravitational force on a 1-kilogram mass under standard gravity, equal to exactly 9.80665 N. It is widely used in mechanical engineering, hydraulics, and everyday language in countries that have not fully adopted SI force units. Lifting capacity of hoists, safe working loads of chains and slings, and tensile strengths of ropes and cables are often quoted in kgf or tonnes-force in European and Asian manufacturing contexts. Spring balances and older force gauges are calibrated in kgf.
A 70 kg person weighs approximately 70 kgf. A small hydraulic jack rated at 2 tonnes supports 2,000 kgf.
Newton – Frequently Asked Questions
Why is the newton the SI unit of force instead of the kilogram?
The kilogram measures mass — the amount of matter in an object — while the newton measures force, which depends on both mass and acceleration (F = ma). A 1 kg object weighs about 9.81 N on Earth but only 1.62 N on the Moon, even though its mass stays the same. The SI system keeps mass and force as separate quantities to avoid the confusion that plagued older systems like the kilogram-force.
How many newtons of force does a human bite exert?
An average adult bite force is about 500–700 N, concentrated on the molars. Clenching hard can reach 900 N in some individuals. For comparison, a saltwater crocodile tops 16,000 N — roughly 20 times a strong human bite. Dentists use newton measurements to design crowns and implants that withstand these chewing forces.
What is the relationship between newtons, joules, and watts?
A joule is one newton applied over one meter (J = N·m), and a watt is one joule per second (W = J/s = N·m/s). So if you push with 10 N over 5 meters you do 50 J of work, and if that takes 2 seconds you exert 25 W of power. These three units form the backbone of mechanical energy calculations in SI.
How much force in newtons does gravity exert on a 1 kg object?
Standard gravity accelerates a 1 kg mass at 9.80665 m/s², producing a force of exactly 9.80665 N. In everyday approximations, engineers round this to 9.81 N or even 10 N for quick mental arithmetic. The precise value matters when calibrating load cells, defining the kilogram-force, or performing high-accuracy aerospace calculations.
Why do physicists use newtons while everyday life uses kilograms for weight?
In daily conversation, saying "I weigh 70 kilograms" conflates mass and weight because gravity is roughly constant on Earth's surface. Physicists distinguish the two: your mass is 70 kg everywhere, but your weight is about 686 N on Earth and 113 N on the Moon. The newton keeps calculations correct wherever gravity varies — essential for aerospace, geophysics, and precision engineering.
Kilogram-force – Frequently Asked Questions
Why do some countries still use kilogram-force instead of newtons?
Many countries in Europe and Asia adopted kgf in engineering and industry before SI became dominant. Crane ratings, hydraulic press capacities, and elevator load limits were standardized in kgf and remain labelled that way on existing equipment. Rewriting decades of documentation and re-stamping machinery is costly, so kgf persists in practice even where SI is officially mandated.
How do you convert kilogram-force to newtons?
Multiply kilogram-force by 9.80665 to get newtons. So 1 kgf = 9.80665 N, and 100 kgf = 980.665 N. For quick estimates, multiply by 9.81 or roughly 10. This conversion factor is simply the standard acceleration due to gravity in m/s².
What is the difference between kilogram-force and kilopond?
They are the same unit. Kilopond (kp) was the name used in Germany, Scandinavia, and other European countries, while kilogram-force (kgf) is the internationally recognized term. Both equal the gravitational force on 1 kg at standard gravity. ISO 80000-4 deprecates both in favor of the newton, but kgf remains common in Asian and European industrial contexts.
Why is kilogram-force problematic in engineering calculations?
Using kgf conflates mass and force, leading to errors when gravity varies or when applying F = ma. Engineers must insert a gravitational constant (gₙ = 9.80665 m/s²) to convert between mass and force, which SI avoids by using separate units — kilograms for mass and newtons for force. Mistakes in this conversion have caused real-world structural miscalculations.
What are typical kilogram-force values in everyday life?
A 70 kg adult weighs about 70 kgf. A firm handshake exerts roughly 10–15 kgf. A bicycle tire inflated to 6 bar exerts about 4.5 kgf per cm² on the rim. These values feel intuitive because they numerically match familiar masses, which is precisely why kgf remains popular in non-technical contexts despite SI deprecation.