kilogram (kg)

The kilogram (kg) is the basic unit of mass in the International System of Units (SI), used worldwide to measure how heavy an object is. It is currently defined by a precise constant in physics: it is based on the Planck constant, a fundamental value in quantum physics. Traditionally, one kilogram was represented by a platinum-iridium alloy cylinder stored in France. The kilogram helps us compare and quantify the weight of objects accurately, whether small like a paperclip or large like a car. Its consistent definition ensures precise measurements across science, industry, and everyday life.