Convert grams to milligrams instantly. Enter a value below, or use the formula and reference table further down the page.
In practice
Grams to milligrams multiplies by 1,000, since a gram is a thousand milligrams. It is the conversion that matters for medicine, supplements and food additives, where doses are tiny: 0.5 g is 500 mg and a 0.25 g tablet is 250 mg. Because errors of a factor of ten or a thousand can be dangerous, always check the unit printed on the label and never assume. For anything medical, rely on the prescriber's or pharmacist's instructions and use this conversion only to understand the figures on the packet.
How to convert grams to milligrams
Multiply the value by 1000.
mg = g × 1000Example: 10 g = 10000 mg.
Grams to Milligrams conversion table
| Grams (g) | Milligrams (mg) |
|---|---|
| 1 g | 1000 mg |
| 2 g | 2000 mg |
| 3 g | 3000 mg |
| 4 g | 4000 mg |
| 5 g | 5000 mg |
| 10 g | 10000 mg |
| 15 g | 15000 mg |
| 20 g | 20000 mg |
| 25 g | 25000 mg |
| 50 g | 50000 mg |
| 100 g | 100000 mg |
Frequently asked questions
How many milligrams is 1 gram?
1 gram equals 1000 milligrams.
What is the formula to convert g to mg?
To convert g to mg, multiply the value by 1000. The full formula is: mg = g × 1000.
How do I convert milligrams back to grams?
Use the same calculator above and type your value into the milligrams field instead — it converts in both directions. Or use the reverse formula: g = mg ÷ 1000.
Is the g to mg conversion exact?
The conversion factor used here (1000) is the standard internationally defined value. Results on this page are rounded to four decimal places for readability.