Specific Gravity Calculator (SG = ρ / ρ_ref)
Specific Gravity Calculator (SG = ρ / ρ_ref)
Specific gravity (also called relative density) is a dimensionless ratio comparing a substance's density to that of a reference material - almost always water (1000 kg/m³) for liquids and solids, or air for gases. Because it's a ratio rather than a raw density, specific gravity immediately tells you whether something floats or sinks in the reference fluid, without needing to remember any units. Choose the variable you need, enter the other two known values, and this calculator solves for the third.
- SG = ρ_substance / ρ_reference, so aluminum (2700 kg/m³) compared to water (1000 kg/m³) has a specific gravity of 2700/1000 = 2.7.
- A specific gravity greater than 1 means the substance is denser than the reference (and sinks in it), while less than 1 means it's less dense (and floats) - ice at SG ≈ 0.92 floats in water, which is why icebergs float.
- Specific gravity is used constantly in practical fields - winemaking and brewing (measuring sugar content via must/wort density), battery maintenance (checking electrolyte charge state), and mineralogy (identifying rocks and gems by density ratio) all rely on it.
How do I calculate specific gravity?
Divide the substance's density by the reference density (usually water, 1000 kg/m³): SG = ρ_substance / ρ_reference. Aluminum at 2700 kg/m³ has SG = 2700/1000 = 2.7.
Why is water used as the reference for specific gravity?
Water has a round, easy-to-remember density of 1000 kg/m³ (1 g/cm³) at 4°C, making it a convenient universal baseline - a specific gravity above 1 sinks in water, below 1 floats.
Specific Gravity Calculator (SG = ρ / ρ_ref)
Specific gravity (also called relative density) is a dimensionless ratio comparing a substance's density to that of a reference material - almost always water (1000 kg/m³) for liquids and solids, or air for gases. Because it's a ratio rather than a raw density, specific gravity immediately tells you whether something floats or sinks in the reference fluid, without needing to remember any units. Choose the variable you need, enter the other two known values, and this calculator solves for the third.
- SG = ρ_substance / ρ_reference, so aluminum (2700 kg/m³) compared to water (1000 kg/m³) has a specific gravity of 2700/1000 = 2.7.
- A specific gravity greater than 1 means the substance is denser than the reference (and sinks in it), while less than 1 means it's less dense (and floats) - ice at SG ≈ 0.92 floats in water, which is why icebergs float.
- Specific gravity is used constantly in practical fields - winemaking and brewing (measuring sugar content via must/wort density), battery maintenance (checking electrolyte charge state), and mineralogy (identifying rocks and gems by density ratio) all rely on it.
How do I calculate specific gravity?
Divide the substance's density by the reference density (usually water, 1000 kg/m³): SG = ρ_substance / ρ_reference. Aluminum at 2700 kg/m³ has SG = 2700/1000 = 2.7.
Why is water used as the reference for specific gravity?
Water has a round, easy-to-remember density of 1000 kg/m³ (1 g/cm³) at 4°C, making it a convenient universal baseline - a specific gravity above 1 sinks in water, below 1 floats.