Case 1
- Density of the substance
- 789kg/m³
- Density of the reference
- 1000kg/m³
0.7890
Open with these valuesSpecific Gravity Calculator
0.7890× water
Result: 0.7890 × waterSpecific gravity is one density divided by another, so it has no units: ethanol at 789 kg/m³ against water at 1000 gives 0.789. Below 1 the substance floats in water, above 1 it sinks. It is not the same as specific weight, which is a force per cubic metre and does depend on gravity.
Worked examples
Case 2
- Density of the substance
- 916.7kg/m³
- Density of the reference
- 1000kg/m³
0.9167
Open with these valuesCase 3
- Density of the substance
- 13534kg/m³
- Density of the reference
- 1000kg/m³
13.5340
Open with these valuesHow it's calculated
SG = ρ substance ÷ ρ reference
- StepEnter the density of your substance in kilograms per cubic metre.
- StepLeave the reference at 1000 kg/m³ for water at 4 °C, or change it.
- ResultRead the ratio: under 1 it floats in the reference, over 1 it sinks.
Reference table
| Substance, reference | Substance | Specific gravity |
|---|---|---|
| 789, 1000 | Ethanol — floats | 0.789 |
| 916.7, 1000 | Ice — floats, just | 0.9167 |
| 1000, 1000 | Water against itself | 1 |
| 2700, 1000 | Aluminium — sinks | 2.7 |
| 13534, 1000 | Mercury — sinks | 13.534 |
| 19300, 1000 | Gold — sinks | 19.3 |
Questions
How do I calculate specific gravity?
Divide the density of your substance by the density of a reference substance. For liquids and solids the reference is water at 4 °C, 1000 kg/m³. Ethanol at 789 kg/m³ therefore has a specific gravity of 0.789.
What is specific gravity?
Specific gravity, also called relative density, is the ratio of a substance's density to the density of a reference substance. It is dimensionless, because it divides one density by another. It tells you how heavy a material is compared with water.
Does a specific gravity above 1 sink or float?
Above 1 the substance is denser than water and sinks in it; below 1 it is less dense and floats. Ice at 0.9167 floats, ethanol at 0.789 floats, and mercury at 13.534 sinks.
What is the difference between specific gravity and density?
Density is mass per unit volume and carries units such as kg/m³, while specific gravity is a ratio of two densities and has none. Because it compares against a known reference, the number is the same whether you measure in kg/m³ or g/cm³.
Which reference density should I use?
For liquids and solids use water at 4 °C, 1000 kg/m³, where water reaches its maximum density. For gases, air at standard conditions is normally used instead. Always state the reference, since the same substance gives a different figure against a different one.
Sources and last check
Information, not professional advice.