How many grams are in one kilogram?

In the metric system, the prefix "kilo-" signifies a factor of one thousand. Therefore, one kilogram is equal to one thousand grams. This is a fundamental concept in metric measurements that helps in converting between different units of mass.

When considering the other responses, they do not reflect the correct conversion. For instance, 100 grams represents just one-tenth of a kilogram, whereas 500 grams is half of a kilogram. Similarly, 1500 grams exceed the one kilogram measure, illustrating that a kilogram is distinctly defined as 1000 grams. Understanding these conversions is essential for accurately measuring weights in various practical contexts.