You're Wondering Whether a Metal Bar Is Solid Gold or Fake Tungsten
Density is the mass per unit volume of a substance. Metals have different densities: gold is 19,300 kg/m³, while tungsten (often used to fake gold bars) is 19,250 kg/m³—nearly identical! But other metals are very different: aluminum is 2,700 kg/m³, iron is 7,874 kg/m³. Knowing a material's density helps identify it, predict whether it floats or sinks, and calculate shipping weight from dimensions. This calculator solves the density formula for any variable.
What This Calculator Does
This calculator computes density from mass and volume, or finds the missing variable. You provide any two of three quantities (mass, volume, density) and it calculates the third. It also includes a database of common material densities (water, metals, plastics, gases) for quick reference. It converts between metric and imperial units and shows whether a substance floats or sinks in water.
How to Use This Calculator
Mass (m): Enter the total mass in kilograms (kg), grams (g), pounds (lb), or other units.
Volume (V): Enter the total volume in cubic meters (m³), cubic centimeters (cm³), liters (L), cubic feet (ft³), gallons, or other units.
Density (ρ or D): Enter the mass per unit volume. Common units are kg/m³, g/cm³, lb/ft³, or g/mL.
Enter any two values, and the calculator solves for the third. Select a material from the database to see typical density values and compare your measured values.
The Formula Behind the Math
Density is defined as mass per unit volume:
ρ = m / V
Where:
Rearranging to solve for each variable:
m = ρ × V (mass equals density times volume)
V = m / ρ (volume equals mass divided by density)
Worked Example:
A metal cube has sides of 5 cm. When weighed, it measures 1,175 grams. Is this solid gold or another metal?
The measured density (9.4 g/cm³) is close to copper (8.9 g/cm³) or a copper alloy. It's not gold or aluminum. Without more testing, you can't identify the exact alloy, but density narrows it down.
Our calculator does all of this instantly, but now you understand exactly what it's computing.
Material Selection and Engineering
Engineers choose materials based on strength-to-weight ratio. Aluminum is light (2.7 g/cm³) but strong, so airplanes use aluminum frames. Steel is denser (7.85 g/cm³) but cheaper and stronger in certain applications. Titanium is expensive (4.5 g/cm³) but used in aircraft engines for its strength at high temperature. Density is a key property in material selection.
Floating and Sinking
An object floats if its density is less than the fluid it's in. Wood floats because its density (typically 0.4–0.9 g/cm³) is less than water (1.0 g/cm³). Aluminum sinks in water (2.7 g/cm³ > 1.0 g/cm³) but floats in mercury (13.5 g/cm³). This principle is essential for ships, submarines, balloons, and buoyancy calculations.
Shipping and Logistics
When calculating shipping costs, dense items cost more to transport. A cubic meter of iron (7,850 kg) is much heavier than a cubic meter of styrofoam (20 kg). Density determines whether a shipment is "weight-limited" (charges by actual weight) or "space-limited" (charges by volume). Bulk cargo companies track density to optimize loading.
Quality Control and Authenticity
Density is a simple but effective quality check. Counterfeit materials often have different densities from genuine ones. Fake precious metals, adulterated oils, and diluted beverages can be detected by density measurements. Water quality is monitored by density (salt water is denser than fresh water, for instance).
Tips and Things to Watch Out For
Units must be consistent. If volume is in cm³, mass should be in grams. If volume is in m³, mass should be in kilograms. A density of 1 g/cm³ is equivalent to 1000 kg/m³. The calculator handles unit conversion automatically.
Temperature affects density. Most materials expand when heated, so density decreases at higher temperature. Water is a notable exception: it's densest at 4°C, and expands both when heated above 4°C and when frozen. Always note the temperature when specifying density.
Pressure affects density of gases significantly. A gas at higher pressure is denser. For liquids and solids, pressure effects are usually small. Gas density often comes with a specified pressure and temperature.
Density is an intensive property. It doesn't depend on the amount of material. A kilogram of gold and a gram of gold have the same density (19.3 g/cm³), though different masses and volumes.
Porous materials have lower bulk density. A block of wood floats because its bulk density (wood + air in pores) is less than water. The wood cell walls themselves are denser than water, but the pores reduce the overall density. This is why some metals (like foam aluminum) can float.
Frequently Asked Questions
What's the difference between density and specific gravity?
Density is mass per unit volume (absolute). Specific gravity is the ratio of a substance's density to water's density (dimensionless). For water, specific gravity = 1.0. For gold, specific gravity = 19.3 (meaning gold is 19.3 times denser than water).
Why does ice float if solid objects are usually denser than liquids?
Water is unusual. Ice (solid water) has a density of 0.92 g/cm³, while liquid water is 1.0 g/cm³. This happens because water's hydrogen bonding creates a crystalline structure with more space between molecules. Most other substances are denser when solid than when liquid.
How do ships made of steel float?
Steel is denser than water (7.85 g/cm³), so solid steel sinks. But a ship isn't solid steel-it's mostly hollow (interior space). The bulk density of a ship (steel + air) is less than 1.0 g/cm³, so it floats. As long as the ship doesn't leak and the air stays inside, it displaces enough water to float.
What's the densest element?
Osmium (Os) is the densest naturally occurring element at 22.59 g/cm³ (slightly denser than iridium at 22.56 g/cm³). Some artificially created elements (like flerovium) might be slightly denser, but osmium is densest among stable, commonly available elements.
How is density related to pressure?
Density = Mass / Volume. If you compress a gas (decrease volume), density increases. Pressure pushes molecules closer, increasing density. For liquids and solids, density changes very slightly with pressure because they're incompressible. For gases, density is highly sensitive to pressure.
Can density be used to identify unknown materials?
Yes, it's a quick screening test. Measure mass and volume, calculate density, and compare to a reference table. If the measured density matches a known material, it's a strong indicator (though not proof). Many materials have similar densities, so you usually need additional tests (melting point, electrical conductivity, crystal structure, etc.) for definitive identification.
Related Calculators
Use our Pressure Calculator to understand how pressure affects density in gases and liquids. The Molar Mass Calculator relates density to molar concentration in solutions. The Dilution Calculator depends on density to convert between volume and mass. For more physics concepts, explore our Acceleration and Kinetic Energy Calculators.