Density Converter
Compare mass vs volume. Will it sink or float?
Sink or Float?
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Density Converter: Mass, Volume & Buoyancy
Density is one of the most fundamental properties of matter. It determines whether an object feels "heavy" for its size (like gold) or seemingly weightless (like styrofoam).
Our Advanced Density Converter goes beyond simple math. With our built-in "Sink or Float" simulator, you can visualize Archimedes' Principle in action, testing objects against Water, Seawater, Gasoline, and Mercury.
Physics Tools
Buoyancy Engine
Real-time simulation. See if your density value will float or sink in real liquids.
Unified Units
No dropdowns. Edit SI (kg/m³) and Imperial (lb/ft³) units side-by-side.
Material Presets
Quickly load values for Gold, Aluminum, Air, and other common substances.
Understanding Density
The Formula
Density (ρ) is defined as mass per unit volume.ρ = m / V
Common Units
- kg/m³ (SI Standard): Used in physics and engineering. Water is 1,000.
- g/cm³ (CGS System): Commonly used in chemistry. Water is 1.0.
- lb/ft³ (Imperial): Used in the US construction industry. Water is ~62.4.
Archimedes' Principle
Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. This means if an object is lighter than the water it pushes away, it will float.
Frequently Asked Questions
How do I convert kg/m³ to g/cm³?
Divide by 1000. For example, the density of water is 1000 kg/m³. Dividing by 1000 gives you 1 g/cm³. This simple relationship makes mental math easy for metric units.
What is the density of water?
Pure water at 4°C has a density of exactly 1000 kg/m³ (or 1 g/cm³). However, seawater is denser (~1025 kg/m³) due to dissolved salts, which is why it is easier to float in the ocean than in a lake.
Why do huge steel ships float?
Archimedes' Principle. While steel is denser than water (7,850 kg/m³), a ship is not a solid block of steel. It is a shell containing mostly air. The average density of the ship (steel + air + cargo) is less than water, so it floats.
What is specific gravity?
Specific Gravity (SG) is a ratio comparing the density of a substance to the density of water. It has no units. If SG > 1, it sinks. If SG < 1, it floats. For example, Gold has an SG of 19.3.
How do I convert lb/ft³ to kg/m³?
Multiply by approximately 16.018. For example, finding the density of concrete which is typically 150 lb/ft³: 150 × 16.018 = 2402 kg/m³.
Does temperature affect density?
Yes. Generally, as things get hotter, they expand and become less dense. Hot air rises because it is less dense than cold air. Water is unique; it is most dense at 4°C and actually becomes less dense when it freezes into ice, which is why ice floats.