Force converter

A mass of 1 kg weighs 9.80665 N under standard gravity, which is the definition of 1 kilogram-force. The kilogram measures mass and the newton force, so the conversion needs an acceleration; 9.80665 m/s² is the conventional value fixed in 1901, and local gravity differs from it by up to about 0.3%.

Multiply by 4.4482216152605, usually rounded to 4.448. One pound-force is the weight of one pound (0.45359237 kg) under standard gravity, so the factor is exact. A 200 lbf load is 889.64 N, and 1 N is 0.224809 lbf.

101.97 kgf. Multiply kilonewtons by 101.9716, or divide by 0.00980665, to get kilograms-force. A carabiner marked 22 kN is rated to 2,243 kgf, or 4,946 lbf, and a 5 kN anchor to 510 kgf. The factor is exact because the kilogram-force is defined with standard gravity, 9.80665 m/s².

A pound (lb) is mass, 0.45359237 kg; a pound-force (lbf) is the weight of that mass under standard gravity, 4.4482216152605 N. On Earth a 10 lb object weighs about 10 lbf, which is why everyday speech uses one word for both. The poundal, 0.138255 N, is the force that accelerates 1 lb at 1 ft/s².

A 70 kg person weighs 686.47 N under standard gravity (70 × 9.80665), which is 70 kgf or 154.3 lbf. Bathroom scales measure this force and divide by g to display kilograms, so a scale set up for standard gravity reads about 0.3% low at the equator and 0.3% high at the poles.

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 4 worked examples whose answers come from independent sources; for example, “1 kgf in newtons” is checked against 1 kgf = 1 kg × 9.80665 m/s² (standard gravity, CGPM 1901).

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement.