Density Calculator

What density is

Density measures how much mass is packed into a given volume. A liter of water and a liter of air take up the same space, but the water has roughly 830 times more mass. Density is written with the Greek letter rho (ρ):

ρ = m ÷ V

Because it doesn’t depend on the size of the sample, density is a property of the material itself. A paper clip and a steel beam made of the same steel have nearly the same density. That is why measuring density is a simple way to help identify a material, check for impurities, or tell whether something will float.

How to use the density calculator

1. Choose what you want to find: Density, Mass or Volume.
2. Enter the two values you know and pick their units. Mass can be in mg, g, kg, metric tons, ounces, pounds or US tons. Volume can be in mL, L, m³, US fluid ounces, gallons, cubic inches, cubic feet or cubic yards. Density can be in kg/m³, g/cm³, g/mL, kg/L, lb/ft³, lb/in³ or lb/gal.
3. Choose the unit for the answer. Other common units are listed below it.
4. If you know a specific gravity instead of a density, enter it as g/cm³ (or g/mL). The two are numerically equal because water is 1 g/cm³.
5. In the Density mode you also get the specific gravity and whether the object floats or sinks in water. A short table lists the reference materials closest to your value.

How to calculate density by hand

A metal sample has a mass of 540 g. You measure its volume by water displacement: the water level rises from 300 mL to 500 mL, so the volume is 200 mL, which is 200 cm³.

ρ = 540 g ÷ 200 cm³ = 2.7 g/cm³

That is 2,700 kg/m³, very close to aluminum in the table below.

Rearranging the formula

• Mass: m = ρ × V. A 3 L container filled with a liquid of density 1.26 g/cm³ (3,000 cm³) holds 3,780 g, or 3.78 kg.
• Volume: V = m ÷ ρ. 10 kg of lead at 11.35 g/cm³ occupies 10,000 ÷ 11.35 ≈ 881 cm³.

Keeping units consistent

Grams with cubic centimeters give g/cm³. Kilograms with cubic meters give kg/m³. Pounds with cubic feet give lb/ft³. Mixing them, such as grams with liters, gives g/L, which is numerically the same as kg/m³.

Density chart of metals and common materials

Nominal densities from NIST’s X-ray attenuation tables, converted to other units. Real samples vary, especially alloys, plastics and concrete.

Real-life uses

Identifying materials

Jewelers and collectors check whether a “gold” item is solid by measuring its density. Gold, at 19.32 g/cm³, is much denser than common plating metals.

Estimating weight from size

Builders and shippers multiply a volume by a known density to estimate weight before anything is lifted. Concrete at about 2.3 t/m³ means one cubic meter weighs roughly 2.3 metric tons.

Liquids in the kitchen and lab

Density turns volumes into masses. Converting a recipe from cups to grams, or a chemical from milliliters to grams, both rely on it. The volume converter and the weight converter handle the unit side.

Gases

Gas density changes strongly with pressure and temperature. For gases, the ideal gas law calculator relates pressure, volume and temperature.

Common mistakes

• Mixing unit systems. Kilograms divided by cubic centimeters gives a number 1,000 times too small for g/cm³.
• Confusing mL and L. 1 L = 1,000 mL = 1,000 cm³.
• Using outside dimensions of hollow objects. The result is an average density, not the material’s density.
• Forgetting temperature. Liquids and gases expand when heated, so their density falls.
• Treating weight in pounds-force as mass. Use the mass in pounds (lb) when calculating density in lb/ft³.

Glossary

• Specific gravity: density divided by the density of water. It has no units and equals the density in g/cm³.
• Buoyancy: the upward push from a fluid, equal to the weight of the fluid displaced.
• Displacement: measuring an object’s volume by the rise in liquid level when it is submerged.
• Bulk density: mass per volume of a loose material, such as gravel, including the air gaps between pieces.