How to Calculate Density
Density is a fundamental property of matter that describes how much mass is packed into a given volume. It's used to identify materials, predict whether objects float or sink, and solve engineering and chemistry problems.
The Formula
Density = Mass / Volume
D = m / V
Rearrangements:
- Mass = Density × Volume
- Volume = Mass / Density
Step-by-Step Examples
Example 1: A gold bar has a mass of 386 g and a volume of 20 cm³. What is its density? D = 386 / 20 = 19.3 g/cm³ (confirms it's gold—pure gold's density is 19.32 g/cm³)
Example 2: Water has a density of 1 g/cm³. What is the mass of 500 mL of water? m = 1 × 500 = 500 g
Common Densities
| Material | Density (g/cm³) |
|---|---|
| Air | 0.0012 |
| Ice | 0.92 |
| Water | 1.00 |
| Aluminum | 2.70 |
| Iron | 7.87 |
| Copper | 8.96 |
| Lead | 11.34 |
| Gold | 19.32 |
Buoyancy: The Float/Sink Rule
An object floats in a fluid if its density is less than the fluid's density:
- Ice (0.92 g/cm³) < Water (1.00 g/cm³) → Ice floats ✓
- Iron (7.87 g/cm³) > Water → Iron sinks ✓
Unit Conversions
1 g/cm³ = 1 g/mL = 1,000 kg/m³
Be careful with units: if mass is in grams and volume is in cm³, density is in g/cm³.
Use our density calculator for any mass and volume combination.