A gram is one thousandth of a kilogram.
Grams to Kilograms Converter — g to kg
Convert Gram (g) to Kilogram (kg) using the exact conversion factor (1 gram = 0.001 kilogram). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Grams to Kilograms converter
Converter
Mass/Weight Converter
Convert SI mass, imperial weight, jewelry, atomic, and astronomy mass units.
Context values
Some unit families need one extra value for a physically accurate result.
Kilogram is 1000 gram units.
Result = input x 0.001 / 1.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Grams to Kilograms
Weight conversions between Gram and Kilogram come up constantly in everyday commerce, shipping, and cooking, since US packaging is usually labeled in pounds while most of the rest of the world uses kilograms. Gram is typically associated with standard small-mass unit worldwide, while Kilogram is typically associated with used as the standard mass unit in nearly every country except the United States and a few others that primarily use the pound..
Formula
kilograms = grams × 0.001
This factor comes from each unit's defined relationship to the category's base unit: 1 gram equals 0.001 base units, and 1 kilogram equals 1 base unit, so dividing one by the other gives the direct gram-to-kilogram factor of 0.001.
Simple example
1 g × 0.001 = 0.001 kg
1 gram = 0.001 kilograms.
Real-world example
50 g × 0.001 = 0.05 kg
50 grams = 0.05 kilograms.
Conversion table
| Gram (g) | Kilogram (kg) |
|---|---|
| 1 g | 0.001 kg |
| 5 g | 0.005 kg |
| 10 g | 0.01 kg |
| 25 g | 0.025 kg |
| 50 g | 0.05 kg |
| 100 g | 0.1 kg |
Reverse conversion: Kilogram to Gram
0.001 kg × 1000 = 1 g
0.001 kilograms = 1 gram.
grams = kilograms × 1000
For a page dedicated to this direction, see Kilogram to Gram.
Gram vs. Kilogram
| Aspect | Gram | Kilogram |
|---|---|---|
| Family | SI derived (metric prefix) unit | SI base unit |
| Typical use | Cooking and nutrition labeling worldwide (including in the US, alongside ounces) | Pricing and labeling goods sold by weight in retail and commodity trade |
| Where it's used | Standard small-mass unit worldwide | Used as the standard mass unit in nearly every country except the United States and a few others that primarily use the pound. |
Understanding the Gram
Gram (g) measures mass. A gram is one-thousandth of a kilogram, the SI base unit of mass. It is classified as a SI derived (metric prefix) unit.
Where it's used: Standard small-mass unit worldwide
Uses of the Gram today
- Cooking and nutrition labeling worldwide (including in the US, alongside ounces)
- Precious metal and small-item weighing
- Scientific and laboratory measurement
History of the Gram
Originally defined in 1795 as the mass of one cubic centimeter of water, the gram follows directly from the kilogram (1/1000 of it) under the modern SI system, inheriting the kilogram's various historical and current definitions.
Historical origin. Gram was not the invention of a single named person; it developed through the process described above.
Understanding the Kilogram
Kilogram (kg) measures mass. The kilogram is the SI base unit of mass; every other SI mass unit is a decimal multiple or fraction of it. It is classified as a SI base unit.
Where it's used: Used as the standard mass unit in nearly every country except the United States and a few others that primarily use the pound.
Uses of the Kilogram today
- Pricing and labeling goods sold by weight in retail and commodity trade
- Dosing calculations in medicine, especially for pediatric and weight-based prescriptions
- Structural and material specification in metric-system engineering
- Scientific measurement of mass across chemistry, physics, and materials research
History of the Kilogram
The kilogram's direct predecessor was the 'grave,' defined by the French Academy of Sciences in 1793 as the mass of one cubic decimeter of water at its temperature of maximum density. Because 'grave' echoed the aristocratic title 'graf,' revolutionary France's decree of 18 Germinal, Year III (7 April 1795) renamed the system: the gram became the reference unit, defined as the mass of one cubic centimeter of water at the melting point of ice, and the kilogram — one thousand grams — took over the grave's practical role.
Turning that water-based definition into a physical object required real experimental work: chemist Louis Lefèvre-Gineau was tasked in 1795 with measuring precisely how much a cubic decimeter of water weighed, and former royal jeweller Marc-Étienne Janety then fabricated a platinum cylinder to embody that measured mass. Deposited in the French National Archives in 1799, it became known as the Kilogramme des Archives.
The metric system spread unevenly — Napoleon briefly restricted its use — but France made it compulsory in 1840, and the 1875 Metre Convention (signed by seventeen nations including the US) established the BIPM and a shared international prototype. The platinum-iridium International Prototype of the Kilogram, adopted in 1889 and nicknamed 'Le Grand K,' served as the world's mass reference for over a century.
On 20 May 2019, the kilogram was redefined by fixing the Planck constant at exactly 6.62607015 × 10⁻³⁴ joule-seconds, so it can now be realized in a laboratory (via a Kibble balance) without reference to any physical object.
Historical origin. Kilogram was not the invention of a single named person; it developed through the process described above.
Gram — sources
- BIPM — The kilogram (SI base unit) — Basis for the gram as 1/1000 of the kilogram.
Kilogram — sources
- BIPM — The kilogram (SI base unit) — Official definition and history since the 2019 redefinition.
- NIST — Kilogram: The Past — History of the kilogram standard from the grave to the International Prototype Kilogram.
- SI Brochure, 9th edition (2019), Appendix 2 — BIPM — Official text of the Planck-constant-based definition of the kilogram.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilograms are in 1 gram?
1 gram equals 0.001 kilograms, using the exact defined conversion factor rather than an estimate.
How do I convert gram to kilogram?
Multiply the gram value by 0.001. The converter above does this instantly to whatever precision you set.
How do I convert kilogram back to gram?
Use the reverse factor: 1 kilogram equals 1,000 grams. You can also use the swap control in the converter above to flip the direction instantly.
What is a gram?
Gram (g) measures mass. A gram is one-thousandth of a kilogram, the SI base unit of mass. It is classified as a SI derived (metric prefix) unit.
What is a kilogram?
Kilogram (kg) measures mass. The kilogram is the SI base unit of mass; every other SI mass unit is a decimal multiple or fraction of it. It is classified as a SI base unit.
Is the gram to kilogram conversion exact?
Yes. Both gram and kilogram are defined by fixed standards rather than physical artifacts, so the factor of 0.001 used above is exact to as many digits as you choose to display.
Where is the gram still used today?
Standard small-mass unit worldwide