Force Converter

About this Force Converter

The Force Converter translates force values between common metric and imperial units. It is useful for mechanical specifications, load references and engineering calculations that present force in different systems.

The newton, the standard scientific unit of force, is defined as the force needed to accelerate a 1 kilogram mass at 1 meter per second squared, while pound-force and kilogram-force are older units still common in some engineering and everyday contexts.

For related tasks, try Pressure Converter, Energy Converter or Power Converter.

How the calculation works

Conversions use the newton as the internal base unit. Kilogram-force represents the force exerted by standard gravity on one kilogram of mass.

How to use it

1. Enter a force value.
2. Choose source and target units.
3. Convert to see the equivalent force.

Practical example

1 pound-force is approximately 4.44822 newtons.

1 newton equals about 0.2248 pound-force, so a force of 100 newtons, roughly the weight of a 10 kg object under standard gravity, converts to approximately 22.48 pound-force.

Things to double-check

Kilogram-force is sometimes confused with kilograms of mass, but they measure fundamentally different things; kilogram-force is a unit of force, while a kilogram is a unit of mass, so converting between them assumes standard Earth gravity.

Newtons, pound-force and kilogram-force

One newton is about 0.2248 pound-force and about 0.10197 kilogram-force. One kilonewton is 1,000 newtons. The weight of a 1 kg mass on Earth is about 9.80665 newtons, so a 75 kg person weighs roughly 735.5 newtons, or 75 kilogram-force. Kilogram-force is not an official SI unit but is still found in older specifications and in everyday speech, where people say kilograms for weight.

Mass and weight

Mass is how much matter an object has and is measured in kilograms, while weight is the force of gravity on that mass and is measured in newtons. A person's mass stays the same on the Moon, but their weight there is only about one sixth. Using kilogram-force blurs this difference, because it equals the weight of one kilogram at standard gravity. When you calculate forces in engineering, use newtons so that the units combine properly.

Where forces appear

Engineers use kilonewtons for loads on beams and foundations, and ratings for climbing equipment, such as carabiners, are given in kilonewtons. Typical climbing carabiners are rated at about 20 to 25 kilonewtons along the strong axis. Vehicle and aircraft engines are described by thrust in newtons or pounds-force. Manufacturers in different regions use different units, so a converter helps when you compare data sheets.

Safety and accuracy

For anything where a failure could cause injury, such as lifting gear, ropes or structural parts, use the rated values from the manufacturer and relevant standards, and apply the safety factor they require. A converted number is only as good as the original figure. Pay attention to the direction of the force, the conditions of the rating and any derating for age or wear. A calculator is for checking units, not for certifying equipment.

From force to pressure

Force becomes pressure when it is spread over an area: pressure equals force divided by area. A person weighing about 735 newtons standing on both feet with a total contact area of 0.04 square metres exerts about 18.4 kilopascals. If the same weight rests on two small heels with a total area of 2 square centimetres, the pressure rises to about 3.7 megapascals, which is why narrow heels can damage floors. Engineers use the same idea to size foundations, bolts and tyres, and converting units keeps the calculation consistent.

Typical forces for scale

Some reference values help you judge a result. A force of 1 kilonewton is about 102 kilograms-force, so a rope with a breaking strength of 20 kilonewtons can hold about 2 tonnes-force before failing. A person pressing on a bathroom scale shows their weight in kilograms, but the actual force on the scale is that mass times 9.81, in newtons. A car door closing, a hand squeeze and a hammer blow differ by large factors, so always check the unit and the conditions in a specification.

Worked examples

A bag of 20 kilograms hanging from a hook exerts a force of about 196 newtons, since the weight is mass times 9.81. A pull of 250 pounds-force equals about 1,112 newtons, because one pound-force is 4.448 newtons. A force of 3.5 kilonewtons is 3,500 newtons, or about 357 kilograms-force. To check a result, remember that 1 kilogram-force is about 9.8 newtons, so multiplying kilograms-force by 10 gives a quick estimate in newtons. If a calculator result differs by a lot from that estimate, recheck the units you chose.

Force, mass and acceleration

Newton's second law says that force equals mass times acceleration. A car of 1,200 kilograms accelerating at 3 metres per second squared needs a net force of 3,600 newtons. A person who weighs 70 kilograms exerts about 687 newtons on the floor when standing still, but more when jumping or landing. Because forces add as vectors, two forces that pull in opposite directions partly cancel. This principle underlies everything from the design of lifts to the way tyres grip the road, and it explains why a newton is defined as the force that gives one kilogram an acceleration of one metre per second squared.

Torque and pressure are different

Force is often confused with related quantities. Torque is a turning force and is measured in newton-metres, not newtons: a wrench of 0.3 metres with a pull of 100 newtons produces 30 newton-metres. Pressure is force divided by area, measured in pascals. A force of 600 newtons on an area of 0.01 square metres is 60 kilopascals. Always check which quantity a specification refers to, because a torque rating of a bolt and a load rating of a bracket are not interchangeable even though both involve newtons.

Ratings, safety factors and dynamic loads

Equipment is rated for a safe working load, which is lower than its breaking strength. A rope with a breaking strength of 20 kilonewtons might have a working load of 4 kilonewtons, using a safety factor of 5. Moving or falling loads create forces larger than the weight alone: stopping a falling 80 kilogram person can produce several times their static weight in force. Always use equipment and ratings approved for the purpose, follow the manufacturer's instructions and inspect for wear. A converter can change units, but it cannot certify that equipment is safe.

Key terms explained

A newton is the force that gives a one kilogram mass an acceleration of one metre per second squared. A kilonewton is a thousand newtons. A pound-force is the force of gravity on a one pound mass at the surface of the earth, and a kilogram-force is the force of gravity on a one kilogram mass. Weight is the force of gravity on a mass, and mass is the amount of matter. Torque is a turning effect, and pressure is force per area.

Rules of thumb and quick checks

One kilogram-force is about 9.81 newtons, so multiply kilograms-force by ten for a rough estimate in newtons. One pound-force is about 4.45 newtons, and one newton is about 0.225 pound-force. A mass of 100 kilograms weighs about 981 newtons, or 0.98 kilonewtons. For safety ratings, check the working load limit, not the breaking strength, and remember that moving or falling loads create larger forces than the static weight.

Frequently asked questions