Milligrams to Grams
Convert milligrams to grams in your browser. The SI prefix milli means one thousandth, so 1 mg is exactly 0.001 g.
g = mg ÷ 1000
NIST SP 811 (2008), Table 5, SI prefixes — milli denotes the factor 10^-3, so 1 mg = 10^-6 kg
Supplement labels, tablet strengths and nutrition panels are written in milligrams, while kitchen scales and recipes work in grams. Both sit on the same metric ladder, so the conversion is a move of the decimal point by three places. The prefix milli means one thousandth, which makes the factor a definition rather than a measurement, and nothing is rounded on the way.
How it is calculated
g = mg ÷ 1000
The SI prefix milli stands for the factor 10⁻³, so a milligram is a thousandth of a gram and a millionth of a kilogram. Dividing by 1000 is exact, and the same rule works the other way: multiply grams by 1000 to get milligrams.
Source: NIST SP 811 (2008), Table 5, SI prefixes — milli denotes the factor 10^-3, so 1 mg = 10^-6 kg
Common values
| milligrams | grams |
|---|---|
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 50 | 0.05 |
| 100 | 0.1 |
| 250 | 0.25 |
| 500 | 0.5 |
| 1,000 | 1 |
| 2,500 | 2.5 |
| 5,000 | 5 |
Questions people ask
- How many milligrams are in a gram?
- Exactly 1000. The prefix milli means one thousandth, so one gram is 1000 milligrams and one kilogram is a million milligrams. A reading of 500 mg is half a gram, and 50 mg is 0.05 g.
- Is a milligram the same as a millilitre?
- No. A milligram measures mass and a millilitre measures volume, and turning one into the other needs the density of the substance. Liquid medicines carry both on the label: the milligrams are the amount of the active ingredient, the millilitres are how much liquid it comes in.
- What is the difference between mg and µg?
- A factor of a thousand. The prefix micro, symbol µ, stands for 10⁻⁶, so a microgram is a thousandth of a milligram and a millionth of a gram. Vitamin labels use both, and reading one as the other is an error of a thousand times.
Related tools
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Tonnes to Kilograms
Convert metric tonnes to kilograms. A tonne is exactly 1000 kg, which is neither the 2000 lb short ton nor the 2240 lb long ton.
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