Density converter
Convert density between kg/m³, g/cm³, lb/ft³ and more, with specific gravity, a floats-or-sinks check and a mass calculator.
Density result
Density
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Enter a value to see if it floats.
- Specific gravityRelative to water
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Mass from volume
Mass equals density times volume. The density here follows the converter above; change it to try a different material.
Mass
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Common material densities
Select a row to load it into the converter above.
| Material | kg/m³ | g/cm³ |
|---|---|---|
| Water (4°C) | 1,000 | 1.000 |
| Seawater | 1,025 | 1.025 |
| Air (15°C, sea level) | 1.225 | 0.001225 |
| Helium (0°C) | 0.1786 | 0.0001786 |
| Ice | 920 | 0.920 |
| Ethanol | 789 | 0.789 |
| Gasoline | 750 | 0.750 |
| Diesel | 850 | 0.850 |
| Mercury | 13,600 | 13.6 |
| Platinum | 21,450 | 21.45 |
| Osmium (densest natural element) | 22,590 | 22.59 |
| Lithium (lightest metal) | 534 | 0.534 |
How it works
Density conversion expresses mass per unit volume across units like kg/m³, g/cm³ and lb/ft³, with water at 4°C having a density of exactly 1 g/cm³ (1,000 kg/m³) as the universal reference point for specific gravity.
- Pick a material or type a value
Choosing a material fills the value and unit for you.
- Read every unit at once
Select any result to copy it.
- Check specific gravity
Above 1 sinks in water, below 1 floats.
Specific gravity and why ice floats
Specific gravity is the ratio of a substance's density to the density of water at 4°C (1,000 kg/m³). It has no unit. A specific gravity above 1 means the material sinks in water, below 1 means it floats. Gold has a specific gravity of 19.3, so it sinks fast. Oak wood is about 0.75, so it floats with about a quarter of its volume above the surface.
Water is unusual because it becomes less dense when it freezes. Liquid water is about 1,000 kg/m³ while ice is about 920 kg/m³, roughly 8% less dense. Most substances get denser when they solidify, but water's crystal lattice takes up more space. That is why ice floats, which matters ecologically: lakes freeze from the top down, insulating the liquid water underneath so aquatic life can survive winter.
Osmium is the densest natural element
Osmium is the densest naturally occurring element at 22,590 kg/m³ (22.59 g/cm³), just ahead of iridium at 22,560 kg/m³. A liter of osmium weighs 22.59 kg (49.8 lb). Tungsten, at 19,300 kg/m³, has almost exactly gold's density, which is why tungsten-filled fakes can pass a casual weight check.
Frequently asked questions
How do I convert kg/m³ to g/cm³?
Divide kg/m³ by 1,000 to get g/cm³. Since 1 m³ equals 1,000,000 cm³ and 1 kg equals 1,000 g, the factor is 1,000,000 divided by 1,000, which is 1,000. Water's density of 1,000 kg/m³ equals 1.000 g/cm³. Gold, 19,300 kg/m³, equals 19.3 g/cm³. Air, 1.225 kg/m³, equals 0.001225 g/cm³. Going the other way, multiply g/cm³ by 1,000.
What is specific gravity and how does it relate to density?
Specific gravity is the ratio of a substance's density to the density of water, 1 g/cm³ at 4°C. It has no unit. A specific gravity greater than 1 means the material sinks in water, less than 1 means it floats. Examples: ice (0.92) floats, aluminum (2.7) sinks, oak wood (about 0.75) floats, lead (11.34) sinks heavily.
Why does ice float on water if it is the same substance?
When water freezes, it forms a crystal lattice that is less dense than liquid water. Ice density is about 920 kg/m³ versus liquid water's 1,000 kg/m³, so ice is about 8% less dense. This is unusual: most substances become denser when they solidify. The fact that ice floats is ecologically important, since lakes freeze from the top down, insulating the liquid water below and letting aquatic life survive.
What is the densest naturally occurring element?
Osmium is the densest naturally occurring element at 22,590 kg/m³ (22.59 g/cm³), just ahead of iridium at 22,560 kg/m³. Gold is 19,300 kg/m³ and lead is 11,340 kg/m³. A liter of osmium would weigh 22.59 kg (49.8 lb). Tungsten, at 19,300 kg/m³, is nearly identical to gold's density, which is why tungsten-filled fakes can fool a casual check.
How do you calculate the mass of a liquid from its volume using density?
Mass equals volume times density. To find the mass of 5 liters of gasoline (about 750 kg/m³, or 0.75 kg/L): 5 times 0.75 equals 3.75 kg. For seawater (1,025 kg/m³): 5 L equals 5.125 kg. This is useful for shipping calculations, fuel weight planning and chemistry. Water's convenient density of 1 kg/L (1 g/mL) makes it the easiest benchmark, which the mass calculator above uses by default.