Density Calculator
Calculate density from mass and volume.
Try an example
5,000 kg/m³
About this calculator
What Is Density?
Density is how much mass a material packs into a given volume. It is written with the Greek letter ρ (rho) and defined as ρ = m ÷ V: mass divided by volume. Dense materials such as lead feel heavy for their size, while light ones like foam or cork feel the opposite. Enter any two of density, mass and volume in this density calculator and it returns the third, so you can identify a material, estimate the weight of an object or work out the volume you need.
Rearranging the Density Formula
- Density = Mass ÷ Volume
- Mass = Density × Volume
- Volume = Mass ÷ Density
A block of metal with a mass of 540 g and a volume of 200 cm³ has a density of 2.7 g/cm³ — which is aluminum. A 2 m³ concrete slab with a density of 2,400 kg/m³ weighs 4,800 kg.
Worked Example
An object with a mass of 10 kg and a volume of 0.002 m³ has a density of 5,000 kg/m³ (5 g/cm³) — denser than water, so it would sink.
Units Matter
Density can be written in many units — kg/m³, g/cm³, g/mL, kg/L, lb/ft³, lb/in³ — so be careful that mass and volume are in matching units before you divide. The most important conversion: 1 g/cm³ = 1,000 kg/m³. Water at 4°C is about 1 g/cm³ (1,000 kg/m³), which is why water is the usual reference point for relative density, or specific gravity.
Typical Densities
- Air (at sea level): about 1.2 kg/m³
- Wood (oak): roughly 600–900 kg/m³
- Water: 1,000 kg/m³
- Aluminum: 2,700 kg/m³
- Steel: about 7,850 kg/m³
- Lead: 11,340 kg/m³
- Gold: 19,300 kg/m³
What Changes Density
Temperature and pressure affect density, though only slightly for solids and liquids. Gases are the big exception: raising the pressure squeezes a gas into a smaller volume and always increases its density, while heating it usually makes it expand and become less dense. That is why hot air rises and why a hot-air balloon floats.
Why Density Is Useful
Density tells you whether an object floats (it floats if its density is below the fluid's), helps identify unknown materials, and is key in engineering, shipping, cooking, geology and chemistry. Pair it with the Pressure Calculator for fluids, the Molarity Calculator for solutions, and the Concrete Calculator for weights of building materials.
Worked example
An object with a mass of 10 kg and a volume of 0.002 m³ has a density of 5,000 kg/m³ (5 g/cm³) — denser than water, so it would sink.
Frequently asked questions
How does density determine whether something floats?
An object floats in a fluid if its density is less than the fluid's density — water has a density of about 1,000 kg/m³ (1 g/cm³), so anything less dense than that floats, and anything denser sinks.
Why do the two units (kg/m³ and g/cm³) matter?
They're just different scales for the same measurement — g/cm³ is more commonly used for everyday materials (water is exactly 1 g/cm³), while kg/m³ is the standard SI unit used in most engineering and scientific contexts.
