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Grams to milligrams (g to mg)

To convert grams to milligrams (g to mg): one gram is 1,000 milligrams, so 0.5 g is 500 mg.

Swap units: mg to g

Notice: Not for calculating medication doses. Incorrect dosing can cause serious injury. Follow the label or the directions of a pharmacist or physician.

In milligrams500 mg

Conversion factor Exact by definition: within the metric system every step is a power of ten.
1 gram = 1,000 milligrams
The other way
1 milligram = 0.001 grams
Working
0.5 x 1,000 = 500
0.5 g in every unit
500 mg 0.5 g 0.0005 kg 5.0000e-7 t 0.017637 oz 0.0011023 lb 0.000078737 st 5.5116e-7 ton 7.7162 gr 0.32151 dwt 0.016075 oz t 0.0013396 lb t
grams to milligrams
gmg
11,000
22,000
55,000
1010,000
2525,000
5050,000
100100,000

How the Unit Converter works

One gram is exactly 1,000 milligrams, by the prefix. Milli is a thousandth.

Worked through: 0.5 g x 1,000 = 500 mg.

Going the other way, one milligram is 0.001 grams.

For mental arithmetic: Add three zeros. 0.5 g is 500 mg.

The unit one step below is the microgram, a thousandth of a milligram. Its symbol begins with the Greek letter mu, which handwritten can be mistaken for an m, so medication-safety guidance recommends writing 'mcg' instead of the symbol: the two units differ by a factor of one thousand. Labels mix the units within a single panel: protein in grams, sodium in milligrams, some vitamins in micrograms, so comparing two of them means converting first. 2.3 g and 2,300 mg are the same quantity.

Precision is worth matching to the input. A measurement given as 0.001 g carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.

Unit Converter FAQ

How many milligrams are in a gram?

1,000. One gram is exactly 1,000 milligrams, by the prefix. Milli is a thousandth.

What is 0.5 g in milligrams?

500 mg. Multiply by 1,000: 0.5 g x 1,000 = 500 mg.

How do I convert milligrams back to grams?

Divide by 1,000, or equivalently multiply by 0.001. One milligram is 0.001 grams. The two factors are reciprocals, so you only need to remember one of them.

Is there a quick way to do this in my head?

Add three zeros. 0.5 g is 500 mg. It is close enough for everyday use.

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