Densidade Relativa
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
dr = ρ/1000
About this calculator
The relative density (dr) calculator determines the ratio between the density of a substance and the density of pure water at 4°C, which is 1000 kg/m³. This dimensionless quantity is widely used in engineering, chemistry, and physics to compare material densities relative to water. The calculation is simple: enter the density of the material in kg/m³ and obtain the relative density value.
The operation is based on the formula dr = ρ / 1000, where ρ is the density of the substance in kg/m³. For example, if a liquid has a density of 1200 kg/m³, its relative density is 1.2, indicating it is 20% denser than water. This metric is useful for predicting buoyancy: substances with dr < 1 float on water, while dr > 1 sink.
When to use? In laboratories to characterize samples, in the food industry to check solution concentration, or in naval engineering projects to calculate buoyancy. Cautions: water density varies with temperature and salinity; for accurate results, use distilled water at 4°C as reference. Ensure that the entered density is in the same unit (kg/m³).
This tool is useful for students and professionals who need quick calculations without consulting tables. Remember that relative density is different from absolute density; the former is dimensionless and comparative. Avoid confusing it with specific weight or specific mass.
Frequently asked questions
What is the difference between relative density and absolute density?
Absolute density is mass per unit volume (kg/m³), while relative density is the ratio of the substance's density to that of water, being dimensionless.
Can I use seawater as reference?
No, the standard reference is pure water at 4°C. Seawater has a different density due to salt, which would alter the result.
What does relative density greater than 1 mean?
It means the substance is denser than water and tends to sink. For example, dr = 2 indicates twice the density of water.
How to convert relative density to absolute density?
Multiply the relative density by 1000 kg/m³. Example: dr = 1.5 results in an absolute density of 1500 kg/m³.
Does relative density vary with temperature?
Yes, because the density of both the substance and water changes with temperature. For accurate comparisons, maintain the standard temperature of 4°C.