How this calculator works
Specific gravity compares a substance density with a reference density. For liquids and solids the reference is usually water, often at 4 C. Enter the reference condition explicitly when precision matters. The ratio has no units and does not change with the local gravitational acceleration.
Formula
SG = rho / rho_reference.
Worked example
A material at 800 kg/m3 compared with water at 1000 kg/m3 has SG = 0.8. SG = 2.7 corresponds to 2700 kg/m3 with that reference.
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Frequently asked questions
Does specific gravity have units?
No. The density units cancel in the ratio.
Is the water reference always exactly 1000?
No. Water density changes with temperature and pressure. 1000 kg/m3 is a convenient rounded value near 4 C.
Will SG below one always float?
A simple solid generally floats in the reference liquid if its effective average density is lower, but surface effects and trapped air can also matter.