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Density calculator: density, mass or volume

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Enter two of mass, volume and density to find the third. The calculator converts grams, cm³ and litres for you and shows the working with the equation students learn at GCSE and IGCSE:

ρ=mV\rho = \frac{m}{V}

where ρ\rho (the Greek letter rho) is density, mm is mass and VV is volume.

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Rearranging the equation

To findUse
Densityρ=m÷V\rho = m \div V
Massm=ρ×Vm = \rho \times V
VolumeV=m÷ρV = m \div \rho

Example: a block has a mass of 500 g and a volume of 250 cm³. ρ=500÷250=2\rho = 500 \div 250 = 2 g/cm³, which is 2,000 kg/m³.

kg/m³ and g/cm³

Both units are common. To convert, 1 g/cm³ = 1,000 kg/m³. Water has a density of about 1,000 kg/m³ (1 g/cm³). If you're given mass in grams and volume in cm³, it's often easiest to work in g/cm³ and convert at the end, which is what the calculator lets you do with the "Show in" option.

Measuring density

  • Regular solid: measure the sides with a ruler to work out the volume, and find the mass on a balance.
  • Irregular solid: lower it into a measuring cylinder (or a displacement can) of water. The rise in water level is the object's volume.
  • Liquid: find the mass of an empty measuring cylinder, add a known volume of liquid, and find the mass again. The difference is the liquid's mass.

These are standard practicals in both GCSE and IGCSE courses.

Will it float?

An object floats in a liquid if its density is less than the liquid's, and sinks if it's greater. The same idea tells you which of two liquids that don't mix will float on the other. Ice floats on water because it is slightly less dense than liquid water.

Common mistakes

  • Mixing units, such as grams with m³. Convert first.
  • Forgetting that 1 m³ = 1,000,000 cm³ (not 100 cm³).
  • Writing the equation upside down. A heavy object in a small space is dense, so mass goes on top.

See our guide on density for more examples and exam questions.

Frequently asked questions

What is the density of air?

About 1.2 kg/m³ at room temperature and normal pressure, around 800 times less dense than water.

How do you find the density of an irregular object?

Find its mass on a balance, then its volume by displacement: lower it into water and measure how much water it pushes out. Divide the mass by the volume.

What is the formula for density?

Density = mass ÷ volume (ρ = m ÷ V). In SI units, density is in kg/m³.

How do you convert g/cm³ to kg/m³?

Multiply by 1,000. For example, 2.7 g/cm³ = 2,700 kg/m³.

What is the density of water?

About 1,000 kg/m³, or 1 g/cm³. It varies slightly with temperature.

Is anything I type sent to a server?

No. The calculation runs in your browser and nothing is stored.

Sources

  1. GCSE Physics (8463) specification: subject content. AQA.
  2. Cambridge IGCSE Physics 0625 syllabus for 2026, 2027 and 2028. Cambridge International.

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