Density tells you how much mass is packed into each cubic metre of a material. A dense material has a lot of mass in a small volume. You calculate it with the equation: density = mass ÷ volume, or ρ = m ÷ V. Here ρ (the Greek letter rho) is the density in kilogram per cubic metre (kg/m3), m is the mass in kilogram (kg) and V is the volume in cubic metre (m3).
Worked example: a metal block has a mass of 12 kg and a volume of 0.002 m3. Its density is 12 ÷ 0.002 = 6000 kg/m3.
The equation can be rearranged. To find the mass, multiply the density by the volume. To find the volume, divide the mass by the density. Water has a density of 1000 kg/m3, so 3 m3 of water has a mass of 3000 kg.
Always check your units first. If a volume is given in cm3, convert it to m3 using 1 m3 = 1 000 000 cm3. For example, 100 cm3 is 0.0001 m3. If a mass is given in grams, divide by 1000 to get kilogram.