Understanding Density (ρ = m/V)
Density is mass per unit volume — a measure of how much matter is packed into a given space. Dense materials have more mass for the same volume. Density explains why iron sinks in water (density 7,874 kg/m³) but wood floats (density typically 400–900 kg/m³). Density is used in materials science, geology, fluid mechanics, and even cooking.
Google ad
Formula
Density Calculator
Calculate density, mass, or volume using ρ = m/V.
Google ad
Worked Example
Given:
Related Calculators
FAQs
Why does ice float on water?
Ice is less dense than liquid water — 917 kg/m³ vs 1,000 kg/m³ for water. This unusual property occurs because ice forms a hexagonal crystal lattice with hydrogen bonds that spaces molecules further apart than in liquid water. This is why lakes freeze from the top down, protecting aquatic life below.
What is relative density (specific gravity)?
Relative density compares a substance's density to that of water (1,000 kg/m³ or 1 g/cm³). Relative density = density of substance ÷ density of water. A substance with relative density > 1 sinks in water; < 1 floats. Relative density has no units.
How is density used in geology?
Geologists measure rock density to identify minerals and study Earth's interior. The Earth's average density is 5,515 kg/m³, much higher than surface rocks (~2,700 kg/m³), indicating a dense metallic core. Density measurements from seismic waves help map Earth's internal layers.