How to Calculate Relative Density Percentage

How to calculate the relative density percentage

The specific gravity is really important in many fields. Like students conduct experiments in labs or engineers want to control the product quality, knowing the way to compute relative density percentage is a must. This comprehensive guide is very detailed, it explains all the important things related to this measurement, like why it is important, how we can do it, and the steps we should follow so that we get the correct results.

What is Relative Density Percentage?

The percentage of relative density, which is commonly known as the specific gravity, is used to compare the density of one material to another. Generally, water is used as a reference substance for this comparison. It gives important information about the density of the stuff, helping with all kinds of scientific and industrial studies.

Significance of Relative Density Percentage

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The relative density percentage is really useful in different subjects like Chemistry, Physics, Geology and Engineering. In order to achieve the quality of the manufactured supplies, it plays a significant role in identifying fraudulent and impure substances. In addition, it is used to evaluate the physical attributes of a material and ensure the production process meets the established benchmarks.

How to calculate relative density percentage?

  1.  Archimedes’ Principle Method
    This is a traditional way to determine the buoyancy of an object in a liquid. I can calculate the relative density percentage by comparing buoyant forces in air and the fluid.

  2. Pycnometer Method
    Yeah so this method uses a pycnometer, which is like a small container that you know the exact volume of. You measure the mass of the empty container, the mass of the container with the substance you’re testing, and the mass of the container with a known substance, and then you can calculate the density of the thing you’re testing. It’s pretty cool.

  3. Hydrometer Method
    Its ultimate goal is to measure the degree of density of liquids in comparison with each other and their surrounding environment. To determine the relative density percentage, you just need to put the hydrometer into the substance of interest and check the scale.

Step-by-Step Guide: Calculating Relative Density Percentage

Step 1: Gather Materials
Get the tools needed depending on the selected technique, which may involve using a pycnometer, hydrometer, or other equipment.

Step 2: Record Initial Measurements
Please record the initial measurements needed for the chosen procedure, including the weight of empty containers and the weight of the measured substance.

Step 3: Perform Calculations
Make sure to use the specific calculations as per the selected method. Comparing volumes, buoyant forces and readings on a hydrometer scale can help to identify the density of a liquid.

Step 4: Determine the Relative Density Percentage
By following these steps, we can easily calculate the relative density percentage of a substance.

Step-by-Step Guide: How to calculate Relative Density Percentage

Example 1: Pycnometer Method

Given Data:

  • Mass of empty pycnometer (m₁) = 25.0 g
  • Mass of pycnometer filled with substance (m₂) = 45.0 g
  • Mass of pycnometer filled with water (m₃) = 40.0 g
  • Volume of pycnometer (V) = 30.0 mL


  1. Calculate the mass of the substance (m) using the formula: $$ 

  2. Calculate the mass of water displaced (Δm) using the formula:

    Δm=m3m1 Δm=40.0g25.0g=15.0g
  3. Calculate the density of the substance (ρ) using the formula:

    $$  \rho = \frac{20.0g}{30.0mL}=0.6667g/mL$$
  4. Calculate the relative density percentage using the formula:


    , where


    is the density of water (1.0 g/mL).


Example 2: Hydrometer Method

Given Data:

  • Reading on the hydrometer scale for the substance (S) = 0.850
  • Reading on the hydrometer scale for water (W) = 1.000


  1. Calculate the relative density of the substance (RD) using the formula:

    RD=SW RD=0.8501.000=0.85
  2. Calculate the relative density percentage using the formula:

These examples illustrate the step-by-step calculations for two common methods of determining relative density percentage. Keep in mind that precision in measurements is crucial for accurate results.

Troubleshooting and Common Mistakes

Inaccuracies in Measurements:
It’s really important to be precise when measuring and weighing volumes because even the smallest error can result in a completely different outcome.

Contamination Concerns:
Don’t forget to be careful while using the pycnometer method since contamination is always a concern. Please make sure to clean and dry all equipment prior to and after every measurement.


Q1: What is the significance of relative density percentage in everyday life?
A1: Relative density percentage is vital in various applications, from assessing the purity of substances in pharmaceuticals to ensuring compliance with quality standards in the manufacturing of materials.

Q2: Can relative density percentage be greater than 1?
A2: Yes, a relative density percentage greater than 1 indicates that the substance is denser than the reference substance (usually water).

Q3: How does temperature affect relative density measurements?
A3: Temperature can influence the density of substances, so it’s crucial to account for temperature variations in measurements or use standardized conditions.

Q4: Are there alternative methods for calculating relative density percentage?
A4: While the mentioned methods are common, other techniques, such as displacement methods, can also be employed based on the nature of the substance.


By learning how to determine relative density percentages, we can gain access to a broad range of scientific and industrial possibilities. Understanding measurements in both physics and manufacturing is critical to their success. Our comprehensive guide will ensure that you have a clear understanding of relative density percentages and the necessary skills to answer any question related to this topic.

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