Convert mg to grams
Type a value in either box, and the answer shows it in the other unit as you type.
- Grams (g)
- 0.001
1 mg = 0.001 g.
Grams (g): 0.001. 1 mg = 0.001 g.
Grams (g) by milligrams (mg)
How to calculate
Converts milligrams (mg) to grams (g) and back, with the exact unit definitions.
Example with the default inputs (Milligrams (mg) 1): 1 mg = 0.001 g.
Formula: g = mg × 0.001
- 1 milligram = 0.001 grams, from the exact definitions in NIST SP 811.
- Exact on the typed decimals: at most 6 decimal places (6 significant digits below 0.0001), rounded half up; an answer of 1 billion or more shows at most 15 significant digits.
Worked examples
Each example is checked against the calculator on every build.
- Milligrams (mg) 1 gives Grams (g) 0.001.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
- Milligrams (mg) 500 gives Grams (g) 0.5.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
- Grams (g) 0.5 gives Milligrams (mg) 500.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
Other questions people ask
How many grams are in a milligram?
1 milligram is 0.001 grams, from the exact unit definitions (NIST SP 811).
How do I convert mg to grams?
Multiply by 0.001: g = mg × 0.001. For example, 1 mg × 0.001 = 0.001 g.
How do I convert grams back to mg?
Multiply by 1,000, or type the grams into the second box and the converter works it out. 1 gram is 1,000 milligrams.
What is 500 mg in grams?
0.5 g: 500 ÷ 1,000.
Do I need the density to convert mg to grams?
No. Both are units of mass, and milli means one thousandth (NIST SP 811), so 1 mg is 0.001 g of any substance.