Measure the density of the substance
Measure the density of the reference substance, usually water
Use the formula: Specific Gravity = Density of substance ÷ Density of reference substance
Ensure both densities are in the same units
For liquids and solids, use water as the reference at a specified temperature
For gases, use air or another specified reference gas
If using mass and volume, calculate density first: Density = Mass ÷ Volume
Divide the substance’s density by the reference density to get the specific gravity
Report the result as a unitless number