How many grams are in a kilogram?
There are 1,000 grams in a kilogram. The prefix kilo means a thousand, so to change kilograms into grams you multiply by 1,000.
The kilogram is the base unit of mass in the International System of Units, or SI. It is the only base unit whose name includes a prefix. A gram was originally defined in the 1790s as the mass of one cubic centimeter of water, so a liter of water has a mass of about one kilogram.
For more than 100 years, the kilogram was defined by a metal cylinder made of platinum and iridium, known as the International Prototype of the Kilogram, kept near Paris. In 2019, scientists redefined the kilogram using a fixed value of the Planck constant, a fundamental number in physics, so it no longer depends on a physical object.
Everyday examples
A paperclip weighs about 1 gram, a slice of bread about 30 grams and a bag of sugar often 1 kilogram. A metric ton, or tonne, is 1,000 kilograms. Smaller units include the milligram, one-thousandth of a gram, which is often used for medicine doses.
Did You Know?
The old prototype kilogram was found to differ by tens of micrograms from its official copies over the years, one reason it was replaced.