How to Convert Grams to Milligrams (g to mg)
Weight units matter at the wet market, where older stalls and Chinese medical halls still quote prices per kati or tael, and when following American recipes in ounces and pounds. This guide shows how to convert grams into milligrams by hand, with examples and a quick-reference table.
The conversion
To convert grams to milligrams, multiply the value by 1,000. To go the other way, divide by the same number (or multiply by 0.001). For a quick estimate, multiply by about 1,000.
Milligrams = grams × 1,000
Worked examples
- 3 g = 3,000 mg
- 12.5 g = 12,500 mg
- 75 g = 75,000 mg
Grams to Milligrams table
| Grams | Milligrams |
|---|---|
| 1 g | 1,000 mg |
| 2 g | 2,000 mg |
| 5 g | 5,000 mg |
| 10 g | 10,000 mg |
| 20 g | 20,000 mg |
| 25 g | 25,000 mg |
| 50 g | 50,000 mg |
| 100 g | 100,000 mg |
| 250 g | 250,000 mg |
| 500 g | 500,000 mg |
| 1,000 g | 1,000,000 mg |
Common questions
Is g to mg exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Milligrams to Grams converter.
Mistakes to avoid
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Background
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
For any value, use the Grams to Milligrams Converter or browse all weight converters.
Run your own numbers: Grams to Milligrams Converter