The SI unit of force, named after the English physicist Isaac Newton, is the newton.
The newton is an SI derived unit with the symbol N. One newton is the force needed to accelerate a one-kilogram mass at one metre per second squared, giving the relationship 1 N = 1 kg·m/s². This definition follows directly from Newton’s second law of motion, commonly written as F = ma.
The unit honors Isaac Newton’s work in classical mechanics, especially his laws of motion and theory of gravitation. The name was formally adopted in 1948, after the MKS system had standardized force as kilogram-metre per second squared.
The newton is often confused with mass. Kilograms measure mass, while newtons measure force; a person’s weight is a gravitational force measured in newtons. At Earth’s conventional gravity, a one-kilogram object weighs about 9.81 N. Other listed units belong to different quantities: the watt measures power, the pascal pressure, and the joule energy.