Specific Gravity Calculator

Specific gravity (often denoted as SG) is a dimensionless quantity defined as the ratio of the density of a substance to the density of a given reference material. When dealing with liquids and solids, water is universally used as the reference standard due to its well-defined properties. The mathematical formula is expressed as:

SG = ρ_substance / ρ_water

Where ρ_substance represents the absolute density of your material and ρ_water represents the density of water (standardly taken as 1.000 g/cm³ or 1000 kg/m³ at 4°C). Because both values share identical units, the resulting specific gravity value has no unit attachment, making direct material comparisons universal across different measurement systems.

Imagine you are working in a laboratory and measuring an unknown mineral sample. You determine that your mineral has an absolute density of 4.5 g/cm³. To find its specific gravity using standard water reference density (1.0 g/cm³), you apply the core equation:

SG = 4.5 g/cm³ / 1.0 g/cm³

Dividing these values yields a specific gravity of 4.5. This means the mineral is four and a half times heavier than an equivalent volume of water, giving you crucial data to help identify the mineral's crystalline structure or composition.

Maintain Consistent Units: Always ensure both the substance density and the reference water density use the exact same unit of measurement (such as kg/m³ or g/cm³) before dividing to avoid calculation errors.

Account for Temperature: Water density changes slightly with temperature. For high-precision laboratory work, ensure your water reference density matches the exact temperature at which the substance density was measured.