How to Find Mass of a Liquid From Density

beakers filled with liquid

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by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated January 04, 2019

Review how to calculate the mass of a liquid from its volume and density. Density is mass per unit volume:

density = mass / volume

You can rewrite the equation to solve for mass:

mass = volume x density

Density of liquids usually is expressed in units of g/ml. If you know the density of a liquid and the volume of the liquid, you can calculate its mass. Similarly, if you know the mass and volume of a liquid, you can calculate its density.

Example Problem

Calculate the mass of 30.0 ml of methanol, given the density of methanol is 0.790 g/ml.

  1. mass = volume x density
  2. mass = 30 ml x 0.790 g/ml
  3. mass = 23.7 g

In real life, you can usually look up the density of commons liquids in reference books or online. While the calculation is simple, it's important to cite answer using the correct number of significant digits.