Density from Specific Gravity Calculator | Calculate Material Density

Density from Specific Gravity Calculator

Calculate Density

Enter the Specific Gravity of the substance and the Reference Density to calculate the substance’s density.

Specific Gravity (SG)

Specific Gravity is unitless. Enter a positive value.

Reference Density Value

Enter the density of the reference substance (e.g., water at 4°C is 1000 kg/m³).

Reference Density Unit

Select the unit for the reference density, or choose ‘Custom’ to use the value entered above as is.

Results:

Density vs. Specific Gravity Chart

Chart showing calculated density at different Specific Gravity values for water at 4°C and 20°C (in kg/m³).

Common Specific Gravity Values

Approximate specific gravity values of common substances relative to water at 4 °C.
Substance	Specific Gravity (approx.)	Reference
Water (4 °C)	1.00	By definition
Water (20 °C)	0.9982	Relative to water at 4 °C
Ice (0 °C)	0.917	Relative to water at 4 °C
Ethanol	0.789	Relative to water at 4 °C
Gasoline	0.71-0.77	Relative to water at 4 °C
Aluminum	2.70	Relative to water at 4 °C
Iron	7.87	Relative to water at 4 °C
Lead	11.34	Relative to water at 4 °C
Gold	19.30	Relative to water at 4 °C
Mercury	13.56	Relative to water at 4 °C

What is Density from Specific Gravity?

Density from Specific Gravity refers to the method of calculating the density of a substance by using its specific gravity (also known as relative density) and the density of a reference substance (usually water at a specific temperature, most commonly 4 °C or 20 °C). Specific gravity is a dimensionless quantity because it’s the ratio of the density of a substance to the density of the reference substance.

Anyone working in fields like chemistry, physics, materials science, engineering (especially fluid mechanics), and geology might need to calculate Density from Specific Gravity. It’s a fundamental concept used to identify substances, determine concentrations, and design various processes and structures involving different materials.

A common misconception is that specific gravity and density are the same. While related, density is a measure of mass per unit volume (e.g., kg/m³ or g/cm³), whereas specific gravity is a ratio of densities and thus has no units. Knowing the specific gravity allows you to easily find the density if you know the reference density, and vice-versa.

Density from Specific Gravity Formula and Mathematical Explanation

The formula to calculate Density from Specific Gravity is straightforward:

Density (ρ) = Specific Gravity (SG) × Reference Density (ρ_ref)

Where:

ρ is the density of the substance you want to find.
SG is the specific gravity of the substance (a dimensionless number).
ρ_ref is the density of the reference substance at a specified temperature (e.g., density of water at 4 °C is approximately 1000 kg/m³ or 1 g/cm³).

The specific gravity definition is the ratio of the density of the substance to the density of the reference substance:

SG = ρ / ρ_ref

By rearranging this, we get the formula for calculating density.

Variables Table

Variable	Meaning	Unit	Typical Range
ρ	Density of the substance	kg/m³, g/cm³, lb/ft³, etc.	0.1 to 22,000+ kg/m³
SG	Specific Gravity	Dimensionless	0.01 to 22+
ρ_ref	Density of reference substance	kg/m³, g/cm³, lb/ft³, etc.	For water: ~1 g/cm³ or 1000 kg/m³

Variables used in the Density from Specific Gravity calculation.

Practical Examples (Real-World Use Cases)

Let’s look at how to calculate Density from Specific Gravity in practice.

Example 1: Finding the density of Aluminum

You know the specific gravity of Aluminum is approximately 2.70. You are using water at 4 °C as the reference, and its density (ρ_ref) is 1000 kg/m³.

Specific Gravity (SG) = 2.70
Reference Density (ρ_ref) = 1000 kg/m³
Density of Aluminum (ρ) = 2.70 × 1000 kg/m³ = 2700 kg/m³

So, the density of Aluminum is 2700 kg/m³.

Example 2: Finding the density of Gasoline

Gasoline has a specific gravity range, let’s say it’s 0.75. We want to find its density in g/cm³ using water at 4 °C as reference (ρ_ref = 1 g/cm³).

Specific Gravity (SG) = 0.75
Reference Density (ρ_ref) = 1 g/cm³
Density of Gasoline (ρ) = 0.75 × 1 g/cm³ = 0.75 g/cm³

The density of this sample of gasoline is 0.75 g/cm³.

How to Use This Density from Specific Gravity Calculator

Enter Specific Gravity (SG): Input the specific gravity value of the substance you are interested in. This is a unitless number.
Enter/Select Reference Density: Input the density of the reference substance (like the density of water) in the “Reference Density Value” field, or select a preset from the dropdown (e.g., water at 4°C or 20°C in different units). If you select a preset, the value will be filled automatically. If you choose “Custom”, the value you entered will be used directly with the selected unit.
Select Reference Density Unit: Choose the units for your reference density from the dropdown. The calculated density will be in these same units.
View Results: The calculator automatically updates and displays the calculated density of your substance, along with the inputs used and the formula.
Use the Chart: The chart visually represents how density changes with specific gravity for common reference densities.
Reset/Copy: Use the “Reset” button to go back to default values or “Copy Results” to copy the output.

The results help you quickly determine the density of a material if you know its specific gravity, which is often easier to find or measure using instruments like a hydrometer.

Key Factors That Affect Density from Specific Gravity Results

Specific Gravity Value: The most direct factor. A higher SG means a higher density for the same reference.
Reference Substance: The density of the reference substance directly scales the result. Water is common, but other liquids or even gases can be references.
Temperature of Reference Substance: The density of the reference substance (especially liquids and gases) changes with temperature. Using the density of water at 4°C vs 20°C will give slightly different results. Our calculator allows selection for water at 4°C and 20°C.
Temperature of the Substance: The specific gravity of the substance itself can change with temperature, although this is usually less significant for solids than for liquids and gases. The SG value used should ideally be for the temperature you are interested in.
Pressure: For gases, and to a much lesser extent liquids, pressure can affect density and thus the specific gravity if the reference is also compressible. For most solids and liquids under normal conditions, pressure effects are negligible.
Purity of Substances: The specific gravity values are for pure substances. Impurities can alter the SG and thus the calculated density. Knowing the material density is crucial for many applications.

Frequently Asked Questions (FAQ)

Q1: What is specific gravity?: A1: Specific gravity, or relative density, is the ratio of the density of a substance to the density of a given reference material (usually water at 4°C for liquids and solids, and air for gases).
Q2: Why is specific gravity unitless?: A2: It’s a ratio of two densities, so the units cancel out (e.g., (kg/m³) / (kg/m³) = 1).
Q3: What is the most common reference substance?: A3: For liquids and solids, water at 4°C (where it is most dense, ~1000 kg/m³) or sometimes 20°C is commonly used. For gases, air at standard temperature and pressure (STP) is often the reference.
Q4: Can I use this calculator for gases?: A4: Yes, if you know the specific gravity of the gas relative to a reference gas (like air) and the density of that reference gas under the same conditions.
Q5: How does temperature affect specific gravity and density?: A5: Most substances expand when heated, decreasing their density and thus potentially changing their specific gravity relative to a reference that also changes density with temperature. It’s important to note the temperatures at which SG and reference density are specified.
Q6: What is a hydrometer?: A6: A hydrometer is an instrument used to measure the specific gravity of liquids based on the principle of buoyancy. It floats higher in denser liquids (higher specific gravity).
Q7: Is specific gravity the same as API gravity?: A7: No. API gravity is a measure commonly used in the petroleum industry, derived from specific gravity but on an inverted scale. A higher API gravity means a less dense petroleum liquid.
Q8: Where can I find specific gravity values for different materials?: A8: Engineering handbooks, chemistry reference tables, and online databases often list the specific gravity of various substances. Our table above gives some examples.

Related Tools and Internal Resources

What is Specific Gravity? – A detailed explanation of the concept of specific gravity and relative density.
Density Calculator – Calculate density from mass and volume, or use this tool if you already know SG.
Volume Calculator – Calculate the volume of various shapes.
Mass Calculator – Calculate mass from density and volume.
Buoyancy Calculator – Explore the principles of buoyancy related to density and specific gravity.
Fluid Dynamics Basics – Learn about the behavior of fluids, where density is a key property.
Material Density Database – A resource for finding the density of various materials.

Calculating Density Using Specific Gravity