Find answers to 40+ common questions about density, formulas, calculations, and applications
The density formula is D = M ÷ V, where:
Density measures how tightly packed matter is in a given space. It's the amount of mass per unit volume.
Density helps identify substances, predict behavior (floating/sinking), design materials, control quality, and solve countless real-world problems in science and engineering.
Mass is the amount of matter (measured with a scale). Density is mass per unit volume (calculated). A kilogram of lead and a kilogram of feathers have the same mass but very different densities.
Density doesn't depend on gravity. Weight does. You'd weigh less on the Moon, but your density stays the same.
Divide mass by volume: D = M ÷ V. For example, 50g ÷ 10mL = 5 g/mL. Use our calculator for quick results.
Use M = D × V. Multiply density by volume. Example: 2.7 g/cm³ × 50 cm³ = 135 grams.
Use V = M ÷ D. Divide mass by density. Example: 100g ÷ 10 g/mL = 10 mL.
Use conversion factors: g/mL × 1000 = kg/m³, or g/mL × 62.4 = lb/ft³. See our units guide for complete factors.
Use algebra to isolate the variable you want. Remember: when moving across the equals sign, flip the operation. See our rearrangement guide.
g/mL, kg/m³, g/cm³, lb/ft³, and lb/in³. Most common in labs: g/mL. SI standard: kg/m³.
Water's density is 1.0 g/mL (at 4°C), 1000 kg/m³, or 62.4 lb/ft³. Water is the reference standard for density.
Because 1 mL = 1 cm³. They're mathematically identical, just expressed differently.
Multiply by 1000. Example: 2.7 g/mL × 1000 = 2700 kg/m³.
Substances less dense than water float; those more dense sink. Oil (0.92 g/mL) floats. Gold (19.3 g/mL) sinks. Use our material density lookup.
Ice (0.92 g/cm³) is less dense than liquid water (1.0 g/cm³), so it floats. Water is unusual—most substances are denser as solids.
Oil density is approximately 0.92 g/mL, making it less dense than water, which is why oil floats on water.
Aluminum density is 2.7 g/cm³ or 2700 kg/m³. It's used in aircraft because it's strong yet relatively light.
Gold density is 19.3 g/cm³, making it one of the densest common metals. This high density is one reason it's valuable.
Steel density is approximately 7.87 g/cm³, making it much denser than aluminum but lighter than lead.
Chemists use density to identify substances, determine concentration, calculate molar mass of gases, and verify product quality. See our chemistry guide.
Engineers use density to select materials, optimize weight, calculate loads, and design structures. Materials chosen based on strength-to-weight ratios.
Population density = Total population ÷ Area. Example: 1,000,000 people ÷ 1000 km² = 1,000 people/km².
Divers adjust buoyancy by managing density to stay at a particular depth. Neutral density (matching water) allows weightless underwater movement.
Yes. Most substances become less dense when heated (particles spread out). Water peaks at 4°C, then becomes less dense above and below that.
Yes, especially for gases. Higher pressure compresses gases into smaller volume, increasing density. Liquids and solids are minimally affected.
STP = Standard Temperature and Pressure (0°C, 1 atm or 25°C, 1 atm). At STP, 1 mole of any ideal gas occupies 22.4 liters.
Air density decreases with altitude (lower pressure). At sea level: 1.2 kg/m³. At Mt. Everest: 0.4 kg/m³.
Specific gravity is density relative to water. Specific gravity = Substance density ÷ Water density. It's dimensionless and easier to compare.
Bulk density includes spaces between particles (for granular materials). Particle density is just the solid material. Bulk < Particle density.
At STP: Molar mass = Density (g/L) × 22.4 L/mol. Example: CO₂ at 1.98 g/L → M = 1.98 × 22.4 = 44.4 g/mol.
A visual aid showing the three forms: D = M/V, M = D×V, V = M/D. Cover the variable you want, the remaining formula shows how to calculate it.
No. Density is always positive. Negative values would be physically meaningless.
Density is intensive. It doesn't depend on amount. All samples of pure water have density 1.0 g/mL, whether 1mL or 1 liter.
Check: (1) Measurement accuracy, (2) Unit conversions, (3) Temperature (affects density), (4) Calculation errors. Even small errors compound.
Yes, always! Units are essential. "2.7" is incomplete. "2.7 g/cm³" is correct and shows your answer's meaning.
Compare to known densities. Water = 1 g/mL. Metals range 2-20 g/cm³. Foams < 0.5 g/cm³. Use our calculator to verify.
Use water displacement: (1) Fill cylinder with water, note level, (2) Add object, (3) New level - old level = volume.
Focus on: (1) The three forms of the formula, (2) Unit conversions, (3) Real-world applications. Practice problems are essential. See our guide.
Our guides include practice problems at multiple difficulty levels. Start with how to calculate density for basics.
Yes! Our density calculator helps verify answers and understand the process. Always show your work.
Mass = amount of matter (measured with scale). Volume = space occupied (measured with ruler or displacement). Density combines both.