Science, Tech, Math › Science Density Worked Example Problem Calculating Density of a Substance Share Flipboard Email Print Density is mass per unit volume of a solid, liquid, or gas. Dave King / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College 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. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 11, 2018 Density is a measure of how much matter is in a space. It is expressed in units of mass per volume, such as g/cm3 or kg/L. This is a worked example of how to calculate the density when given the volume and mass of a substance. Sample Density Problem A brick of salt measuring 10.0 cm x 10.0 cm x 2.0 cm weighs 433 grams. What is its density?Solution:Density is the amount of mass per unit volume, or:D = M/VDensity = Mass/VolumeStep 1: Calculate VolumeIn this example, you are given the dimensions of the object, so you have to calculate the volume. The formula for volume depends on the shape of the object, but it's a simple calculation for a box: Volume = length x width x thicknessVolume = 10.0 cm x 10.0 cm x 2.0 cmVolume = 200.0 cm3Step 2: Determine Density Now you have the mass and the volume, which is all the information you need to calculate density.Density = Mass/VolumeDensity = 433 g/200.0 cm3Density = 2.165 g/cm3Answer:The density of the salt brick is 2.165 g/cm3. A Note About Significant Figures In this example, the length and mass measurements all had 3 significant figures. So, the answer for density should also be reported using this number of significant figures. You'll have to decide whether to truncate the value to read 2.16 or whether to round it up to 2.17.