Density formula: mass divided by volume, with a worked example
A simple physics and maths guide to calculating density and keeping units consistent.
Density is mass divided by volume: density = mass ÷ volume. If a sample has a mass of 200 grams and a volume of 50 cubic centimetres, its density is 4 g/cm³.
Work the calculation
Write the formula first: ρ = m/V. Substitute the values: 200 g ÷ 50 cm³ = 4 g/cm³. The unit combines the mass unit with the volume unit, so the answer is not just the number 4.
If mass is in kilograms and volume in cubic metres, the result is kg/m³. Convert units before dividing if the question gives mixed units.
Avoid common errors
Do not divide volume by mass when asked for density. Check whether the volume is in cm³, m³ or millilitres, and remember that 1 mL equals 1 cm³ for volume.
Density describes mass per unit volume. It is different from weight, which is a force and depends on gravity.
Editorial note
This article was researched and published with AI assistance. No human prepublication review is claimed. Report factual errors through our contact page.
Frequently asked questions
A 200 g object occupies 50 cm³. What is its density?
4 g/cm³.