Relative Density Calculator
To calculate relative density, you need the density of the substance and the density of the reference. Then, divide the substance’s density by the reference density.
Table of Contents
What is Relative Density?
Relative density is defined as the ratio of the density of a substance to the density of a reference substance under the same conditions. It tells you how heavy a material is compared to something you already know, usually water.
In simple words: it is a comparison, not an absolute measurement.
Because it is a ratio, it carries no unit. You will never see “kg/m³” or “g/cm³” after a relative density value. Just a number like 7.85 or 0.6.
Water is the standard reference for solids and liquids. Its density is 1000 kg/m³ or 1 g/cm³ at room temperature. For gases, the reference is usually air.
The term “specific gravity” means the exact same thing. Both are used in physics, chemistry, and engineering. If your textbook says specific gravity, your answer from this tool is still valid.
How to Use the Relative Density Calculator?
Step 1: Enter the Density of Your Substance
Type the density of the material you want to check. You can also select your unit from the dropdown: kg/m³, g/cm³, kg/L, or lb/ft³. Our tool handles the unit conversion automatically.
Step 2: Enter the Density of Reference Material
By default, the reference density is set to 1000 kg/m³, which is water at room temperature. If your problem uses a different reference material like mercury or oil, you can change this value.
Step 3: Click Calculate
Click the Calculate button and your relative density result appears instantly. The tool also tells you whether the substance will float, sink, or suspend in the reference material.
Step 4: Reset and Try Again
No calculation limit. Click Reset and you can start fresh with new values right away.
Example:
The density of iron is 7850 kg/m³. Find its relative density with respect to water.
Solutions:
Enter 7850 in the Substance Density box, keep the unit as kg/m³. The reference density is already set to 1000 kg/m³ (water). Click Calculate.
Result: 7.85
Since 7.85 is greater than 1, the tool tells you iron will sink in water. Your assignment answer is done in under 10 seconds. No formula confusion, no calculation mistake.
What is the Relative Density Formula?
The formula used in this calculator is:
Where:
- ρ substance = Density of the given material
- ρ reference = Density of the reference material (water = 1000 kg/m³ or 1 g/cm³)
Relative Density vs Specific Gravity: Are They the Same?
Yes, they are. Specific gravity and relative density mean the same thing. Both compare a substance’s density to the density of water. Some textbooks use “specific gravity” and others say “relative density.” Both give you the same number using the same formula.
Frequently Asked Questions
Can relative density be less than 1?
Yes, it can. If a substance is lighter than water, its relative density will be less than 1. For example, wood has a relative density of around 0.6, which is why it floats.
Is relative density the same as density?
No, Density is an absolute value with units like kg/m³ or g/cm³. Relative density is a comparison between two densities. It is a ratio, so it has no unit. Density tells you how heavy something is. Relative density tells you how heavy it is compared to a reference.
What happens when relative density equals 1?
When relative density is exactly 1, the substance has the same density as the reference material. It will neither float nor sink. It will suspend neutrally in the fluid. This is also called neutral buoyancy.
Why is water used as the reference material?
Water is the most common liquid on Earth and has a clean, easy-to-remember density of 1 g/cm³ or 1000 kg/m³. It makes comparisons simple and consistent across all fields, from physics to engineering to chemistry.
