Weight & Mass Unit Converter

Understanding Mass vs. Weight in Physics and Commerce

In everyday speech, "mass" and "weight" are often used interchangeably. However, in physics, they describe fundamentally distinct concepts:

• Mass is an intrinsic, fundamental property of matter that measures the amount of substance in an object and its resistance to acceleration (inertia). Mass remains identical anywhere in the universe.
• Weight is the force exerted on that mass by gravity ($W = m \times g$). On Earth, standard gravity is defined as $g = 9.80665\text{ m/s}^2$. On the Moon, an object with a mass of 60 kg still has a mass of 60 kg, but its weight is reduced to approximately 1/6th.

The Modern SI Definition of the Kilogram

For over a century, the kilogram was defined by a physical platinum-iridium cylinder kept in Sèvres, France (the International Prototype of the Kilogram). In May 2019, the General Conference on Weights and Measures redefined the kilogram in terms of fundamental physical constants—specifically by fixing the exact value of Planck’s constant ($h = 6.62607015 \times 10^{-34}\text{ J}\cdot\text{s}$) using a Kibble balance.

Weight Measurement Systems Compared

Weight Conversion Factors Reference Table

Frequently Asked Questions