Density Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
Density is calculated by dividing mass by volume: ρ = m ÷ V. For 1,000 g of water occupying 1,000 cm³, the density is exactly 1 g/cm³.
Explanation
Density (often written ρ, the Greek letter rho) shows how much matter is packed into a given volume: it's what distinguishes, at equal volume, an ice cube from a block of lead. It's calculated simply by dividing a sample's mass by the volume it occupies. Pure water serves as a convenient reference point: its density is about 1 g/cm³ (1,000 kg/m³), a value that also defines a substance's "specific gravity" (the ratio of its density to that of water) — gold, at 19.3 g/cm³, is therefore about 19.3 times denser than water. Be careful not to confuse density with weight: two objects of the same volume but different density don't have the same mass, so not the same weight either (see our weight calculator) — density characterizes the substance itself, independent of quantity or the local strength of gravity.
Example: 1,000 g of water in 1,000 cm³
Inputs
Mass: 1,000 g. Volume: 1,000 cm³.
Calculation
Density = mass ÷ volume = 1,000 ÷ 1,000 = 1.
Result
This water sample's density is 1 g/cm³, the reference value for pure water.
Frequently asked questions
What's the difference between density and specific gravity?
Density is expressed with a unit (g/cm³ or kg/m³) and directly measures mass per unit of volume. Specific gravity is a unitless number that compares this density to that of water (for a solid or liquid): a specific gravity of 19.3 means the substance is 19.3 times denser than water. Numerically, specific gravity therefore matches density in g/cm³, just without the unit.
Why do some objects float and others don't?
An object floats in water if its average density is lower than that of water (about 1 g/cm³), and sinks if it's higher — this is Archimedes' principle. A steel ship floats despite steel's density being far higher than water's, because its hollow shape brings its average density below that threshold.
How do I convert g/cm³ to kg/m³?
Multiply by 1,000: 1 g/cm³ equals exactly 1,000 kg/m³. That's why water's density is expressed equally well as 1 g/cm³ or 1,000 kg/m³, depending on the chosen unit.