Density Calculator UK
Calculate density from mass and volume, and rearrange to find mass or volume from density.
How it works
Enter mass and volume in any consistent units. The calculator divides mass by volume to give density, and also shows how to rearrange the formula to find mass or volume.
Frequently asked questions
What is the density formula?
Density equals mass divided by volume (ρ = m ÷ V). Rearrange it to find mass (m = ρV) or volume (V = m ÷ ρ).
What units is density measured in?
Commonly kilograms per cubic metre (kg/m³) or grams per cubic centimetre (g/cm³). 1 g/cm³ equals 1000 kg/m³.
What is the density of water?
About 1 g/cm³, or 1000 kg/m³, at typical conditions. It is the standard reference for comparing other materials.
Why do some objects float and others sink?
An object floats if it is less dense than the liquid around it and sinks if it is denser. This is why ice floats on water.
How do I find mass from density and volume?
Multiply density by volume. A material at 8 g/cm³ filling 30 cm³ has a mass of 8 × 30 = 240 g.
What is specific gravity?
It is an object’s density divided by the density of water, giving a unitless number. A specific gravity above 1 means the object sinks in water.
The density formula
Density is how much mass is packed into a given volume, written ρ = m ÷ V (density equals mass divided by volume). Enter any two of mass, volume and density and the calculator finds the third by rearranging the same equation.
Common units
Density is usually given in kilograms per cubic metre (kg/m³) or grams per cubic centimetre (g/cm³). Water is the handy reference point at about 1 g/cm³ (1000 kg/m³), so materials denser than water sink and lighter ones float.
Worked example
A metal block with a mass of 240 g and a volume of 30 cm³ has a density of 240 ÷ 30 = 8 g/cm³ — close to iron. To find mass instead, multiply density by volume; to find volume, divide mass by density.
Density explains everyday phenomena: why ice floats (it is less dense than liquid water), why oil sits on top of vinegar, and how engineers choose lightweight but strong materials. Specific gravity is simply density compared with water.
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