Specific Gravity Calculator
Calculate specific gravity from substance and reference densities.
Includes common material SG values and determines whether a substance floats or sinks.
Specific gravity (SG) is a dimensionless ratio that compares the density of a substance to the density of a reference substance — typically water at 4°C (39.2°F), which has a density of exactly 1,000 kg/m³.
The Core Formula:
SG = ρ_substance / ρ_reference
For liquids and solids (referenced to water):
SG = ρ_material / 1,000 kg/m³
For gases, the reference is air at STP (1.225 kg/m³).
Using Archimedes’ Principle (for irregular solids):
SG = Weight in Air / (Weight in Air − Weight in Water)
Worked Example 1 — Liquid sample:
- A 500 mL oil sample weighs 430 g
- Density = 430 g / 500 mL = 0.860 g/cm³
- SG = 0.860 / 1.000 = 0.860 (floats on water — SG < 1)
Worked Example 2 — Irregular solid:
- A rock weighs 250 g in air and 155 g submerged in water
- Buoyant force = 250 − 155 = 95 g equivalent
- SG = 250 / 95 = 2.63 (similar to granite)
Reference Table:
| Material | SG |
|---|---|
| Ice | 0.917 |
| Seawater | 1.025 |
| Concrete | 2.0–2.4 |
| Aluminum | 2.7 |
| Steel | 7.8–8.1 |
| Lead | 11.3 |
| Gold | 19.3 |
| Mercury | 13.6 |
Applications: Used in brewing (alcohol content), mining (ore separation), geology (mineral identification), and fluid dynamics. A hydrometer directly measures SG of liquids.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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