What does 375mg equal in ml?

Answer 1

The volume occupied by 375 milligrams of air and 375 grams of water will clearly be very different. So there is no direct conversion between mass and volume: you need to know the density of the substance to enable you to carry out the conversion.

Some people still believe that there is a conversion in relation to water but that is only approximately true. Until 1964 a litre was defined as the volume of one kilogram of pure water at 4 degrees Celsius and at a pressure of 760 millilitres of Mercury. With that definition a conversion would have been valid - but only for pure water and only under those conditions. In any case that definition of a litre was abandoned in favour of 1 litre =1000 cubic centimetres.