Find a substance’s specific gravity — how many times denser it is than water, the reference every material scientist and geologist compares density against.
How it works
Specific gravity is a substance’s density divided by water’s: SG = density ÷ 1 g/cm³. Because it’s a ratio of two densities, it has no unit — a specific gravity of 2 simply means “twice as dense as water.”
What this does not include
This uses water’s density at 4°C (1 g/cm³) as the fixed reference, the standard convention. It doesn’t account for the substance’s own temperature, which can shift its actual density slightly from a textbook value.
How to use this calculator
- Enter the substance’s density in g/cm³.
- Read off the specific gravity.
A worked example
A substance with density 1.5 g/mL: specific gravity = 1.5 ÷ 1 (water’s density) = 1.5 — it would sink in water.
Mercury at 13.6 g/mL: specific gravity = 13.6 — over 13 times denser than water.
What the variables mean
| Variable | Meaning |
|---|---|
| Density | The substance’s density, in grams per milliliter |
Edge cases worth knowing
Specific gravity is dimensionless, unlike density. Since water’s density is defined as 1 g/mL, specific gravity works out numerically identical to density in g/mL — but as a pure ratio, it has no units at all.
A specific gravity below 1 means the substance floats in water, while above 1 means it sinks — a quick, unit-independent way to compare buoyancy across substances.
Why does mercury have such a high specific gravity?
Mercury is about 13.6 times denser than water because it’s a heavy metal — its atoms pack far more mass into the same volume than water’s light hydrogen and oxygen molecules do.
What does a specific gravity under 1 mean?
The substance is less dense than water and would float — ice, at about 0.92, is a familiar example.
Is specific gravity the same as density?
No — density has units (like g/cm³) and depends on the measurement system used; specific gravity is a unitless ratio to water, so it reads the same regardless of which unit system the original density was measured in.
