Density Calculator
Density is mass per unit volume. This calculator solves for density, mass, or volume when any two values are known, and compares the result to common materials for intuition.
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Formula
ρ = m / V
Density (ρ) equals mass (m) divided by volume (V). In SI: kg/m³. In CGS: g/cm³. Water has a density of 1 g/cm³ = 1,000 kg/m³. Objects denser than water sink; less dense objects float. Specific gravity is the ratio of a material's density to water's density.
How to use the Density Calculator
- 1
Enter your mass
Value should be in g.
- 2
Enter your volume
Value should be in mL (cm³).
- 3
Read your results instantly
Results update in real time as you type.
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Density of common materials
Density varies enormously across materials. Ice: 0.917 g/cm³ (floats on water). Water: 1.0 g/cm³. Aluminum: 2.7 g/cm³. Steel: 7.85 g/cm³. Lead: 11.34 g/cm³. Gold: 19.32 g/cm³. Osmium (densest natural element): 22.59 g/cm³. Air at sea level: 0.00129 g/cm³.
These differences drive many practical decisions. Aluminum's low density (combined with its strength) makes it ideal for aircraft. Tungsten's high density (19.3 g/cm³) and strength make it suitable for armor-piercing projectiles. Aerogels can have densities below 0.002 g/cm³ — nearly as light as air.
Density and buoyancy
An object floats if its average density is less than the surrounding fluid. A steel ship floats not because steel floats, but because the hollow ship displaces enough water to equal its total weight. If you crumple the ship into a solid ball, it sinks — average density exceeds water.
This is Archimedes' Principle: buoyant force = weight of displaced fluid = ρ_fluid × V_submerged × g. A 1 m³ cube submerged in water experiences 9,810 N of upward buoyant force regardless of what it's made of.
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Measuring density in practice
For regular solids, density = mass / (l × w × h). For irregular solids, use water displacement: submerge the object in a graduated cylinder and measure the volume increase. For liquids, fill a known volume and weigh it.
Hydrometers measure liquid density directly — they float higher in denser liquids. Brewers use them to track fermentation (as sugar converts to alcohol, density drops). The Plimsoll line on ships marks the safe loading depth — below a certain waterline, the ship's average density approaches that of water and sinking risk rises.
Tips & Insights
g/cm³ = kg/L
1 g/cm³ = 1 kg/L = 1,000 kg/m³. Water is 1 g/cm³ = 1 kg/L. This makes unit conversion straightforward.
Will it float?
If density < 1 g/cm³ (less than water), it floats. If > 1 g/cm³, it sinks in water. Ice (0.917) floats; most rocks (2.5-3.0) sink.
Temperature affects density
Most materials expand when heated, reducing density. Water is unusual: it's densest at 4°C. Above and below 4°C, water expands — which is why ice floats and ponds freeze from the top down.
Worked Examples
Identifying a metal sample
Density = 386 ÷ 20 = 19.3 g/cm³ — consistent with gold (19.32 g/cm³).
Cooking oil
Density = 460 ÷ 500 = 0.92 g/cm³. Less than water — oil floats, which is why oil and water don't mix.
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Frequently Asked Questions
What is density?
Density is mass per unit volume: ρ = m/V. It tells you how much matter is packed into a given space.
What is the density of water?
1 g/cm³ = 1 kg/L = 1,000 kg/m³ at 4°C. This is the benchmark for specific gravity — materials with density > 1 g/cm³ sink in water.
What is specific gravity?
Specific gravity is the ratio of a material's density to water's density. It's dimensionless. Specific gravity > 1 means denser than water (sinks); < 1 means less dense (floats).
Why does ice float on water?
Ice (0.917 g/cm³) is less dense than liquid water (1.0 g/cm³). Water expands when it freezes, reducing density. This is unusual — most solids are denser than their liquid form.
How do ships made of steel float?
A ship's hull encloses air, making the average density of the ship system much less than water. The ship displaces water equal to its total weight, producing enough buoyancy to float.
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