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Density Calculator

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Enter mass and volume to find density, or use the water displacement method for an irregularly shaped object.

Density Calculator

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Density
2.00 g/cm³
Kg per m³
2,000 kg/m³
Relative to water
2.00x
1 mL of water displaced equals 1 cm³ of object volume, since water's density is almost exactly 1 g/cm³.

The formula

Density = Mass / Volume Water displacement: Volume = Water level after - Water level before
Example

A 500g object with a volume of 250 cm³: density = 500/250 = 2.00 g/cm³. Using displacement instead - water rises from 200mL to 350mL for a 750g object: volume = 150 cm³, density = 750/150 = 5.00 g/cm³.

Step-by-step guide

  1. For a regular shape (where you can measure or calculate volume directly): enter mass and volume.
  2. For an irregular shape: submerge the object in a container of water, and enter the water level before and after - the rise in level equals the object's volume.
  3. Read the density, along with the kg/m³ equivalent and how it compares to water.

Why water displacement works

An object submerged in water pushes aside (displaces) a volume of water exactly equal to its own volume, regardless of its shape - this is the same principle Archimedes is famously said to have used to verify a crown's purity. Since water conveniently has a density almost exactly 1 gram per cubic centimeter, the volume in cm³ is numerically identical to the milliliters of water displaced, making this a simple, practical way to find the volume of oddly-shaped objects without any complex geometry.

Common mistakes

Using an object that floats for the displacement method - it needs to be fully submerged for the displaced volume to equal the object's true volume.
Mixing grams with liters or other mismatched units - keep mass in grams and volume in cm³ (or both in kg and liters) for the result to come out correctly.

Frequently asked questions

Why does density matter?

Density helps identify materials (different substances have distinct, well-documented densities), predict whether something floats or sinks, and is a basic input for countless engineering and science calculations involving weight and volume.

Why is 1 mL of water equal to 1 cm³?

A milliliter is defined as exactly one cubic centimeter of volume - they're literally the same unit under two different names, one used for liquids and one for solid volume.

What does it mean if something has a density less than 1 g/cm³?

It means the object is less dense than water and will float, since water's density is almost exactly 1 g/cm³ - this is why the "relative to water" figure in this calculator doubles as a quick floats-or-sinks check.

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