How much 1 milliliters equal how many millagrams?

The conversion from milliliters (mL) to milligrams (mg) depends on the density of the substance being measured. For water, 1 milliliter is approximately equal to 1000 milligrams, since the density of water is about 1 gram per milliliter. However, for other substances, you would need to know the specific density to make an accurate conversion.