Kilograms and grams
The kilogram is the SI base unit of mass, defined since 2019 by fixing the Planck constant. Body weight, groceries, luggage allowances and most product weights outside the US are given in kilograms.
The gram is one thousandth of a kilogram. Recipes, nutrition labels, postage and small parcels use grams.
Worked example
Convert 2.5 kg: 2.5 × 1,000 = 2,500, so 2.5 kilograms is 2,500 grams. Likewise 2 kg = 2,000 g.
Estimating in your head
The factor is a power of ten, so just move the decimal point 3 places to the right: 2.5 kg = 2,500 g.
Going the other way
To convert grams to kilograms, divide by 1,000 (or multiply by 0.001). The swap button between the boxes opens that page.
How this works
g = kg × 1,000
1 kg = 1 kg and 1 g = 0.001 kg, both by definition, so the factor is their ratio: 1,000 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many grams are in a kilogram?
1 kilogram = 1,000 grams, exactly. The value follows from the unit definitions, so it never changes.
How do I convert kilograms to grams?
Multiply by 1,000. For example, 2 kg × 1,000 = 2,000 g.
What is 10 kg in grams?
10 kg = 10,000 g. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- Federal Register 59-5442 (1959) — Refinement of values for the yard and the pound
- Wikipedia — Avoirdupois system
Reviewed Oct 17, 2026 · test vectors fixtures/units/mass/kg-to-grams/