To convert grams to milligrams, multiply the number of grams per thousand. That is, use the following simple formula:
KMG = Kg * 1000 where
KMG – the number of milligrams

Kg – the number of grams.
For example, the weight of one tablet of activated carbon and 0.25 gram. Therefore, its mass expressed in milligrams is: 0,25*1000=250 (mg).
If the gram amount is an integer, to translate grams into milligrams, just add to it right three zero.
For example, one tablet of ascorbic acid with glucose weighs 1 gram. So its mass in milligrams is: 1 000.
If the quantity of grams is expressed in the form of a decimal fraction, move the decimal point three digits to the right.
For example, the glucose content in one tablet of ascorbic acid with glucose – 0,887 grams. Therefore, in milligrams mass of glucose will be 887 mg.
If the decimal point has fewer than three digits, append the missing digits with zeros.

For example, the content of ascorbic acid in one tablet of ascorbic acid with glucose is 0.1 grams. In milligrams it is – 100 mg (according to the rules, it turns out 0100 mg, but trailing zeros to the left are discarded)..
If all source data specified in grams, and the result should be presented in milligrams, all intermediate calculations spend in grams, and milligrams translate only the result of the computation.
For example, in one pill allochol contains:

- bile dry – 0.08 g,

- dried garlic – 0,04 g

- nettle leaves – 0.005 g,

- activated carbon – 0,025 g.

To calculate: how many milligrams of active substances is contained in one tablet of allohol, add the masses of each component are expressed in grams, and the result is put in milligrams:

0,08+0,04+0,005+0,025=0,15 (g).

0,15*1000=150 (mg).