Why does ice float on water?

Water expands when it freezes — the hydrogen bonds in solid ice form an open hexagonal lattice that takes up more space than liquid water. This makes ice less dense (0.917 g/cm³) than liquid water (1.000 g/cm³), so it floats.

What is specific gravity?

Specific gravity is the ratio of a substance's density to the density of water at 4°C. It is dimensionless and numerically equal to density in g/cm³. Specific gravity > 1 means the substance sinks in water; < 1 means it floats.

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How to Calculate Density, Mass, or Volume — Free (2026)

By Rui Barreira · Last updated: 18 June 2026

Calculate density, mass, or volume from any two known values with the brevio Density Calculator — free, no signup, runs entirely in your browser. Select what you want to solve for, enter the two known values with their units, and get the answer instantly with automatic unit conversion.

Density is one of the most fundamental properties of matter, used in materials science, chemistry, engineering, cooking, and everyday life. The formula is simple — density equals mass divided by volume — but unit conversions can make manual calculations error-prone.

How to Use the Tool

Select what to solve for: density, mass, or volume.
Enter the two known values and select their units from the dropdown menus.
Click Calculate. The tool converts all values to SI units internally, performs the calculation, and shows the result in your chosen output unit.

The Density Formula

The fundamental relationship is: ρ = m / V, where ρ (rho) is density, m is mass, and V is volume.

Rearranged to solve for the other variables: m = ρ × V (mass = density × volume) and V = m / ρ (volume = mass / density).

Common reference densities: water at 4°C = 1.000 g/cm³ (or 1,000 kg/m³); air at sea level = 0.001225 g/cm³; gold = 19.32 g/cm³; aluminium = 2.70 g/cm³; oak wood ≈ 0.70 g/cm³ (floats on water); ice = 0.917 g/cm³ (floats on water because it is less dense than liquid water).

Unit Conversions

The tool handles these unit conversions automatically: mass in kg, g, or mg; volume in m³, cm³, litres, or millilitres; density in kg/m³, g/cm³, or g/mL. Note that g/cm³ and g/mL are numerically identical because 1 cm³ = 1 mL exactly.

Frequently Asked Questions

Why does ice float on water?: Water expands when it freezes — the hydrogen bonds in solid ice form an open hexagonal lattice that takes up more space than liquid water. This makes ice less dense (0.917 g/cm³) than liquid water (1.000 g/cm³), so it floats. This anomalous property is essential for aquatic life: frozen lakes develop an insulating ice layer while water below remains liquid.
What is specific gravity?: Specific gravity is the ratio of a substance's density to the density of water at 4°C. It is dimensionless and numerically equal to density in g/cm³ (since water's density is 1 g/cm³). Specific gravity > 1 means the substance sinks in water; < 1 means it floats.
How do I find the density of an irregular solid?: Use Archimedes' method: weigh the object in air, then weigh it fully submerged in water. The difference in weight equals the weight of displaced water. Since water's density is 1 g/cm³, the volume displaced equals the volume of the object. Then divide mass by volume to get density.

Related tools: Molar Mass Calculator · Unit Converter

Frequently Asked Questions

Why does ice float on water?: Water expands when it freezes — the hydrogen bonds in solid ice form an open hexagonal lattice that takes up more space than liquid water. This makes ice less dense (0.917 g/cm³) than liquid water (1.000 g/cm³), so it floats.
What is specific gravity?: Specific gravity is the ratio of a substance's density to the density of water at 4°C. It is dimensionless and numerically equal to density in g/cm³. Specific gravity > 1 means the substance sinks in water; < 1 means it floats.
What units does the tool support?: The tool handles mass in kg, g, or mg; volume in m³, cm³, litres, or millilitres; density in kg/m³, g/cm³, or g/mL. All conversions are done automatically.