How to Calculate Density
Quick Answer
Density formula: Density = Mass ÷ Volume | ρ = m ÷ V
Common units: g/cm³ or g/mL (chemistry) | kg/m³ (SI standard, engineering) | lb/ft³ (US construction)
Example: A block of wood has a mass of 600 g and a volume of 1,000 cm³. Density = 600 ÷ 1,000 = 0.6 g/cm³. This wood floats on water because its density is below 1 g/cm³.
Density is one of the most fundamental concepts in science. It explains why some objects sink and others float, why different metals feel heavier than others of the same size, and how materials are identified in chemistry and engineering. Use the Density Converter on CalConvs to convert between density units.
The Density Formula in Three Forms
- Density = Mass ÷ Volume (ρ = m ÷ V), find density when you know mass and volume
- Mass = Density × Volume (m = ρ × V), find mass when you know density and volume
- Volume = Mass ÷ Density (V = m ÷ ρ), find volume when you know mass and density
If you know any two of these three quantities, you can find the third.
- Example 1 (find density): Mass = 250 g, Volume = 100 cm³. Density = 250 ÷ 100 = 2.5 g/cm³.
- Example 2 (find mass): Density of iron = 7.87 g/cm³, Volume = 50 cm³. Mass = 7.87 × 50 = 393.5 g.
- Example 3 (find volume): Mass = 1,000 g, Density of water = 1 g/cm³. Volume = 1,000 ÷ 1 = 1,000 cm³ = 1 litre.
Densities of Common Materials
| Material | kg/m³ | g/cm³ |
|---|---|---|
| Air (at sea level) | 1.225 | 0.001225 |
| Water (at 4°C) | 1,000 | 1.000 |
| Seawater | 1,025 | 1.025 |
| Ice | 917 | 0.917 |
| Wood (pine) | 400 to 600 | 0.4 to 0.6 |
| Concrete | 2,000 to 2,400 | 2.0 to 2.4 |
| Aluminium | 2,700 | 2.70 |
| Iron | 7,870 | 7.87 |
| Copper | 8,960 | 8.96 |
| Lead | 11,340 | 11.34 |
| Gold (24K) | 19,300 | 19.30 |
| Mercury (liquid) | 13,534 | 13.534 |
Why Gold Can Be Tested by Density
Pure 24K gold has a density of 19.3 g/cm³. This is more than twice the density of most metals. Even lead (11.34 g/cm³) and silver (10.49 g/cm³) are significantly lighter. This is why measuring density in water is still used to test gold purity.
| Gold Purity | Approximate Density |
|---|---|
| 24K (pure) | 19.3 g/cm³ |
| 22K | 17.7 to 17.9 g/cm³ |
| 18K | 15.2 to 15.9 g/cm³ |
| 14K | 12.9 to 14.6 g/cm³ |
Density Units and Conversions
| Unit | Equivalent |
|---|---|
| 1 g/cm³ | 1,000 kg/m³ = 1 g/mL = 62.43 lb/ft³ |
| 1 kg/m³ | 0.001 g/cm³ = 0.0624 lb/ft³ |
| 1 lb/ft³ | 16.018 kg/m³ = 0.016018 g/cm³ |
Frequently Asked Questions
What is the density of water?
The density of pure water is exactly 1.000 g/cm³ (1,000 kg/m³) at 4°C. Water is slightly less dense at higher temperatures. At 20°C, water is 0.998 g/cm³. Objects with a density less than 1 g/cm³ float on water.
How do I measure the volume of an irregular object?
Use the water displacement method. Fill a measuring cylinder with a known volume of water. Submerge the object fully. The volume of water displaced equals the volume of the object. This method was famously used by Archimedes.
What unit should I use for density?
For everyday science and chemistry: g/cm³. For engineering and physics: kg/m³ (SI standard). For US construction: lb/ft³. All three describe the same property and can be converted using the table above.
Related Tools
- Density Converter: g/cm³, kg/m³, lb/ft³ and more
- Weight and Mass Converter: grams, kilograms, pounds and ounces
- Volume Converter: cm³, litres, ml, gallons and more
- All Unit Converters: 74 converters on CalConvs