There are 1,000 grams in a kilogram. A gram is a metric unit commonly used for measuring the mass of small objects such as small amounts of food and jewelry. Kilograms are typically used for determining the mass of larger objects, such as furniture or a person's body mass.
Units of mass are divided into 1,000 parts. One kilogram has the same mass as one liter or 1,000 grams of water, while a gram is approximately the mass of a single paper clip. Anything that is under a gram is measured in milligrams and micrograms, and anything that weighs more than a thousand kilograms is measured in tons.
The kilogram is the base unit of mass in the International System of Units, and it is the only unit in that system that is defined by a physical object rather than a fundamental physical property that can be reproduced in laboratories.