What is the formula for density?

The formula for density is D = M/V, where D is density, M is mass and V is volume. To find mass, rearrange to M = D × V. To find volume, rearrange to V = M/D. This triangle is fundamental to GCSE physics and chemistry.

What is the density of water?

The density of pure water at 4°C is 1.000 g/cm³ (or 1000 kg/m³). This is the standard reference point for density. At room temperature (20°C) the density of water is approximately 0.998 g/cm³. Seawater is slightly denser at about 1.025 g/cm³ due to dissolved salts.

How do you measure the density of an irregular solid?

To measure the density of an irregular solid: (1) Weigh the object on a balance to find its mass. (2) Fill a displacement can (Eureka can) or measuring cylinder with water and record the initial volume. (3) Submerge the object and record the new volume or collect the displaced water. (4) The volume of the object equals the volume of displaced water. (5) Calculate density using D = M/V. This is the classic GCSE displacement method based on Archimedes' principle.

Why does ice float on water?

Ice floats on water because it is less dense than liquid water. Ice has a density of approximately 0.917 g/cm³, while liquid water at 0°C has a density of about 0.9998 g/cm³. When water freezes, the hydrogen bonds form a hexagonal crystal lattice that holds molecules further apart than in the liquid state, making ice about 9% less dense. This unusual property is vital for aquatic life — ice forms at the surface and insulates the water below.

What are the units of density?

The SI unit of density is kilograms per cubic metre (kg/m³). In chemistry and GCSE physics, grams per cubic centimetre (g/cm³) is commonly used — note that 1 g/cm³ = 1000 kg/m³. Other units include g/mL (equivalent to g/cm³), kg/L, and lb/ft³ (used in imperial systems). For gases, density is often quoted in g/L or kg/m³ because their densities are much lower.

How does temperature affect density?

As temperature increases, most substances expand (their volume increases) while their mass stays the same, so density decreases. This is why hot air rises — it is less dense than cooler surrounding air. For liquids, the relationship is generally linear; water is a notable exception, being densest at 4°C. For gases, density is inversely proportional to temperature (in Kelvin) as described by the ideal gas law PV = nRT. For solids, thermal expansion is smaller but still causes a slight density decrease with rising temperature.

Density Calculator

Mass

Volume

Output unit

Please enter valid positive values for mass and volume.

About the Density Calculator

A density calculator helps you find the density, mass or volume of any substance using the fundamental physics formula.

Formula: Density (ρ) = Mass (m) ÷ Volume (V)
Common units: kg/m³, g/cm³, g/mL, lb/ft³

Frequently Asked Questions

What is density?

Density is the measure of mass per unit volume of a substance. Water has a density of 1 g/cm³ (or 1000 kg/m³) at standard conditions.

How do I calculate volume from density?

Volume = Mass ÷ Density. If you have 500g of a substance with density 2.5 g/cm³, volume = 500 ÷ 2.5 = 200 cm³.

What is the density of common materials?

Water: 1.0 g/cm³, Steel: 7.85 g/cm³, Aluminium: 2.7 g/cm³, Wood (oak): 0.7 g/cm³, Air: 0.0012 g/cm³.

Why is density important?

Density determines whether objects float or sink, affects structural engineering calculations, and is used in chemistry, physics and engineering across the UK.

Density of Common Materials

Material	Density (g/cm³)	Density (kg/m³)
Water (4°C)	1.000	1,000
Air (20°C)	0.0012	1.2
Ice (0°C)	0.917	917
Aluminium	2.70	2,700
Iron	7.87	7,870
Steel	7.85	7,850
Copper	8.96	8,960
Gold	19.32	19,320
Wood (oak)	0.70	700
Concrete	2.30	2,300

What is specific gravity and how does it relate to density?

Specific gravity (SG) is the ratio of a material's density to the density of water (1.0 g/cm³). A specific gravity greater than 1 means the material sinks in water; less than 1 means it floats. For example, steel has SG ≈ 7.85, so it sinks; wood (oak) has SG ≈ 0.70, so it floats. Specific gravity is dimensionless and numerically equal to density expressed in g/cm³.

How do I use density in Archimedes' principle?

Archimedes' principle states that a submerged object experiences a buoyant force equal to the weight of fluid it displaces. If an object's density is less than the fluid's density, it floats. If greater, it sinks.

For example, a steel ship floats because its average density (including air-filled hull) is less than water's density. This principle is used in ship design, submarine ballasting, and determining whether materials will float in chemical processes.

How do I find the density of an irregular solid?

For irregular solids, use water displacement: (1) Weigh the object to find its mass in grams. (2) Fill a measuring cylinder with water and record the initial volume in mL. (3) Submerge the object fully and record the new volume. (4) Volume of object = final volume minus initial volume (in cm³, since 1 mL = 1 cm³). (5) Apply D = M/V. This is the standard GCSE method taught in UK schools and is based on Archimedes' principle.

What is the density of gases compared to liquids?

Gases are far less dense than liquids or solids. Air at sea level is about 1.2 kg/m³, which is roughly 830 times less dense than water (1,000 kg/m³). Gas density varies significantly with temperature and pressure — this is why hot-air balloons rise (hot air is less dense than cooler surrounding air). Natural gas (methane) has a density of about 0.668 kg/m³ at standard conditions, making it lighter than air, which is why gas leaks rise upward.