A gram is one thousandth of a kilogram.
Grams to Milligrams Converter — g to mg
Convert Gram (g) to Milligram (mg) using the exact conversion factor (1 gram = 1,000 milligram). See the formula, worked examples, conversion table, history, and common uses.
Grams to Milligrams converter
Converter
Scientific Units Converter
Convert SI derived units, scientific notation-friendly units, atomic units, and lab measurements.
Context values
Some unit families need one extra value for a physically accurate result.
Milligram is 0.001 gram units.
Result = input x 0.001 / 1e-6.
Mass units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Grams to Milligrams
Gram and Milligram are both scientific-measurement units, spanning everything from atomic and laboratory scales to astronomical distances — the kind of conversion that comes up constantly in physics, chemistry, and astronomy when a result needs to move between conventions used in different subfields. Gram is most often used for cooking and nutrition labeling worldwide (including in the us, alongside ounces).
Formula
milligrams = grams × 1000
This factor comes from each unit's defined relationship to the category's base unit: 1 gram equals 0.001 base units, and 1 milligram equals 0.000001 base units, so dividing one by the other gives the direct gram-to-milligram factor of 1000.
Simple example
1 g × 1000 = 1,000 mg
1 gram = 1,000 milligrams.
Real-world example
10 g × 1000 = 10,000 mg
10 grams = 10,000 milligrams.
Conversion table
| Gram (g) | Milligram (mg) |
|---|---|
| 0.001 g | 1 mg |
| 0.01 g | 10 mg |
| 1 g | 1,000 mg |
| 10 g | 10,000 mg |
| 100 g | 100,000 mg |
| 1,000 g | 1,000,000 mg |
Reverse conversion: Milligram to Gram
1 mg × 0.001 = 0.001 g
1 milligram = 0.001 grams.
grams = milligrams × 0.001
For a page dedicated to this direction, see Milligram to Gram.
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 Milligram (mg)
Milligram is 0.001 gram units.
Gram — sources
- BIPM — The kilogram (SI base unit) — Basis for the gram as 1/1000 of the kilogram.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many milligrams are in 1 gram?
1 gram equals 1,000 milligrams, using the exact defined conversion factor rather than an estimate.
How do I convert gram to milligram?
Multiply the gram value by 1000. The converter above does this instantly to whatever precision you set.
How do I convert milligram back to gram?
Use the reverse factor: 1 milligram equals 0.001 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 milligram?
Milligram (mg) is a unit of scientific units.
Is the gram to milligram conversion exact?
Yes. Both gram and milligram are defined by fixed standards rather than physical artifacts, so the factor of 1000 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
Why does this category span everything from atomic to astronomical scales?
Scientific work spans an enormous range of physical scales, from atomic distances (measured in angstroms or atomic mass units) to interstellar distances (measured in astronomical units or parsecs), so this category groups SI-derived and scale-specific units that researchers commonly need to convert between within their field.