How much does 545 ml weigh?

Answer 1

There can be no conversion.

A millilitre is a measure of volume. The masses of equal volumes of the two substances will depend on the densities of the substances and so will clearly be very different. There is, therefore, no direct conversion between mass and volume. You will then need to multiply the mass by the acceleration due to gravity which is appropriate to the location in question.

Answer 2

That depends what you have in those 545 ml. For example, 545 ml of empty space basically weigh nothing.You need to multiply the volume by the density of the material.