Density Calculator
This density calculator solves ρ = m ÷ V for any unknown. Select whether you want to find density, mass, or volume, enter the two known values with your chosen units, and get instant results with common unit conversions.
Enter known values
Choose which variable to solve for, then fill in the other two.
Understanding density: ρ = m ÷ V
Density measures compactness — how much mass is squeezed into a unit of volume. The three rearrangements of the formula cover every practical case:
ρ = m ÷ V (density from mass and volume)
m = ρ × V (mass from density and volume)
V = m ÷ ρ (volume from mass and density)
Density is the key to identifying unknown materials, understanding buoyancy, and calculating loads in structural engineering. The density of water (1 g/cm³ or 1000 kg/m³) is a useful reference benchmark — materials denser than water sink, less dense ones float.
Frequently asked questions
- What is density?
- Density is the amount of mass packed into a given volume. It is defined as mass divided by volume: ρ = m ÷ V. A material with high density has many particles crammed into a small space (such as lead or gold), while a low-density material has fewer particles per unit volume (such as wood or aerogel). Density is an intensive property — it does not depend on how much of a material you have.
- What is the formula for density?
- Density (ρ, the Greek letter rho) equals mass (m) divided by volume (V): ρ = m ÷ V. Rearranging gives m = ρ × V (to find mass) and V = m ÷ ρ (to find volume). This calculator solves all three forms — select which variable you want to find and enter the two known values.
- What units does density use?
- In SI units, density is expressed in kilograms per cubic metre (kg/m³). In chemistry and everyday life, grams per cubic centimetre (g/cm³) or grams per millilitre (g/mL) are common — note that 1 g/cm³ = 1 g/mL = 1000 kg/m³. The imperial unit is pounds per cubic foot (lb/ft³). The calculator accepts mass in kg, g, lb, or oz, and volume in m³, cm³/mL, L, or ft³.
- What is the density of water?
- Pure water has a density of approximately 1 g/cm³ (1000 kg/m³) at 4 °C, which is its maximum density. At room temperature (20 °C) it is about 0.998 g/cm³. Seawater is slightly denser at roughly 1.025 g/cm³ due to dissolved salts. Ice floats on water because it is less dense (about 0.917 g/cm³) — one of water's unique and life-enabling properties.
- How does density explain whether an object floats or sinks?
- An object floats in a liquid if its average density is less than the liquid's density, and sinks if its average density is greater. A solid steel ball (density ~7900 kg/m³) sinks in water (1000 kg/m³), but a steel ship floats because the hull encloses a large volume of air, bringing the ship's average density below that of water. This is Archimedes' principle in action.
- What are some common material densities?
- Approximate densities: air at sea level 1.2 kg/m³, cork 200 kg/m³, wood (oak) 700 kg/m³, water 1000 kg/m³, concrete 2400 kg/m³, aluminium 2700 kg/m³, steel 7900 kg/m³, copper 8900 kg/m³, lead 11,300 kg/m³, gold 19,300 kg/m³, osmium (densest natural element) 22,590 kg/m³.
- How is density used in science and engineering?
- Density is fundamental in structural engineering (choosing materials for strength-to-weight ratio), fluid mechanics (modelling buoyancy and flow), geology (identifying minerals), food science (measuring sugar or alcohol content), and medicine (bone density scans, blood plasma density). It is also used in quality control to verify material composition without destructive testing.