Formula used
Density to specific gravity: SG = ρsubstance ÷ ρreference
Specific gravity to density: ρsubstance = SG × ρreference
Specific gravity is a ratio, so it has no unit.
How to use this calculator
- Select density-to-specific-gravity or reverse calculation mode.
- Enter the density or specific gravity value.
- Choose the density unit and reference substance.
- Use a custom reference when your standard differs.
- Select precision, notation, and significant figures.
- Add optional comparison materials or batch values.
- Calculate, copy, download CSV, or save as PDF.
Example calculations
| Substance | Density | Reference | Specific gravity |
|---|---|---|---|
| Gasoline | 740 kg/m³ | Water at 4°C | 0.7400 |
| Ethanol | 0.789 g/mL | Water at 4°C | 0.7890 |
| Aluminum | 2700 kg/m³ | Water at 4°C | 2.7000 |
| Mercury | 13.546 g/cm³ | Water at 4°C | 13.5460 |
Common material density reference
| Material | Approximate density | Approximate SG versus water |
|---|---|---|
| Air | 1.225 kg/m³ | 0.001225 |
| Gasoline | 720–760 kg/m³ | 0.72–0.76 |
| Ethanol | 789 kg/m³ | 0.789 |
| Water | 1000 kg/m³ | 1.000 |
| Seawater | 1025 kg/m³ | 1.025 |
| Glycerin | 1260 kg/m³ | 1.260 |
| Aluminum | 2700 kg/m³ | 2.700 |
| Steel | 7850 kg/m³ | 7.850 |
| Copper | 8960 kg/m³ | 8.960 |
| Lead | 11340 kg/m³ | 11.340 |
| Mercury | 13546 kg/m³ | 13.546 |
Values vary with temperature, pressure, purity, composition, and measurement method.
Understanding density and specific gravity
Density describes mass contained within a defined volume. It keeps physical units such as kilograms per cubic meter. Specific gravity compares that density with a chosen reference.
Water is the usual reference for liquids and solids. Dry air is commonly used when comparing gases. The selected reference must match the intended engineering convention.
Temperature can change both substance and reference densities. Water reaches approximately 1000 kilograms per cubic meter near 4°C. Using another temperature slightly changes the final ratio.
A specific gravity below one means lower density than reference. A value above one means greater density than reference. Equality indicates both densities are effectively the same.
Floating predictions require more than density in practical systems. Shape, trapped air, surface tension, and fluid motion can matter. The displayed buoyancy statement is therefore only a guide.
Unit conversion happens before the ratio is evaluated. This prevents errors caused by comparing incompatible density units. The calculator converts every supported unit into kilograms per cubic meter.
Custom references support laboratory and industrial procedures. Enter the reference density measured under your required conditions. Record temperature and pressure beside important reported results.
Batch mode helps compare fuels, metals, chemicals, and samples. Each line can include a name, value, and unit. Results remain tied to the currently selected reference substance.
Significant figures should reflect measurement quality, not screen capability. Excess digits may imply accuracy your instruments cannot provide. Select suitable rounding before sharing calculated results.
Frequently asked questions
What is specific gravity?
Specific gravity is the ratio between a substance density and a selected reference density. It has no measurement unit.
Which reference should I choose?
Use water for most liquids and solids. Use air for gases when that convention matches your application.
Why does water temperature matter?
Water density changes slightly with temperature. That change affects the calculated specific gravity ratio.
Can specific gravity be negative?
Ordinary mass density and specific gravity are not negative. The calculator rejects negative input values.
Does a value below one always float?
It generally indicates lower average density than water. Real floating behavior can also depend on shape and trapped air.
Can I calculate density from specific gravity?
Yes. Select reverse mode, enter specific gravity, choose the reference, and select the desired output unit.
Why are my results different from a handbook?
Reference conditions, purity, pressure, temperature, and rounding may differ. Match all conditions before comparing values.
How does batch input work?
Enter one item per line. You may provide only density, density with unit, or name with density and unit.
Can I export the results?
Yes. Download a CSV file or use the print button to save a PDF through your browser.