A density calculator solves the relation density = mass ÷ volume for whichever variable you don't have. Pick what to solve for, density, mass, or volume, enter the other two, and the calculator returns the third in standard metric units (grams, cubic centimeters, g/cm³).
Useful for chemistry calculations, materials identification (an unknown metal sample's density narrows it down quickly), buoyancy estimates, container sizing, and any setting where two of mass, volume, and density are known and the third is needed.
Key takeaway
Density is a material's fingerprint. Two pure materials with the same density are likely the same substance; two with different densities can't be. This is why ancient civilizations used the "Archimedean test" (water displacement) to identify gold versus cheaper metals, the densities differ enough that even crude measurement reveals counterfeits.
How it's calculated
The three forms:
- Density = Mass ÷ Volume, find density when you have a sample
- Mass = Density × Volume, find weight from a known volume of a known material
- Volume = Mass ÷ Density, find space needed for a known mass
Standard density units:
- g/cm³ (grams per cubic centimeter), most common for solids and liquids in chemistry
- kg/m³, SI standard, used in physics; multiply g/cm³ by 1,000
- lb/ft³, US customary; multiply g/cm³ by 62.43
Common reference densities (g/cm³):
- Water (4°C): 1.000 (definitional)
- Ice: 0.917 (less dense than water, why ice floats)
- Aluminum: 2.70
- Iron / steel: 7.87
- Copper: 8.96
- Lead: 11.34
- Mercury: 13.55
- Gold: 19.32
- Osmium: 22.59 (densest natural element)
Source: Standard physical identity, density = mass ÷ volume
Examples
Find density: 100 g sample, 50 cm³ volume
- Solve for Density
- Mass (g) 100
- Volume (cm³) 50
- Density (g/cm³) 0
A 100 g sample displacing 50 cm³ of water has a density of 2 g/cm³. Roughly the density of pumice or some glasses; light aluminum alloys come in around 2.7. The "g/cm³" number directly tells you the specific gravity (relative to water), 2 g/cm³ is exactly twice as dense as water.
Find mass: 200 cm³ of iron
- Solve for Mass
- Mass (g) 0
- Volume (cm³) 200
- Density (g/cm³) 7.87
200 cm³ of iron (density 7.87 g/cm³) has a mass of 1,574 g (
3.47 lb). For comparison, the same volume of aluminum (2.70 g/cm³) would weigh only 540 g (1.19 lb), almost a third of the iron's weight at the same size. This density gap is why aluminum is preferred over iron for weight-sensitive structures like aircraft and bicycles.
Frequently asked questions
How do I calculate density?
Density = Mass ÷ Volume. Weigh the object on a scale (mass), measure or compute its volume (geometric formula for regular shapes; water-displacement for irregular ones), then divide. Standard units are g/cm³ for solids and liquids. For pure water at 4°C, density is exactly 1.000 g/cm³, a useful reference point for sanity-checking any other density measurement.
What does specific gravity mean?
Specific gravity (SG) is the ratio of a material's density to water's density at a reference temperature. So aluminum's SG is 2.70 (meaning it's 2.70× denser than water); gold's SG is 19.32. SG is dimensionless, no units, just a ratio. It's used widely in mineralogy, brewing (to track sugar concentrations in wort), and battery testing (to track electrolyte density).
How does density relate to floating and sinking?
An object floats if its average density is less than the fluid's; sinks if greater. Pure ice (0.917 g/cm³) floats on water (1.000) because it's less dense. Iron sinks in water but floats on mercury (mercury's density is 13.55, vs. iron's 7.87). Boats float despite being made of dense materials because their average density (steel + air-filled hull) is less than water's. This is Archimedes' principle in action.
How do I find the volume of an irregular object?
Water displacement, the classic "Archimedes" method. Fill a graduated cylinder with water, note the volume. Drop the object in (fully submerged); the new water level minus the old is the object's volume. Works for any shape that doesn't absorb water and doesn't dissolve. For larger objects, use a displacement vessel with a spout, the overflow water collects in a measured container, equal to the object's volume.