How this instrument works
Density is mass packed into a given volume — an intensive property, meaning it does not care how much material you have, only how tightly its mass is arranged. The formula, ρ = m ⁄ V, is a plain ratio: divide the kilograms by the cubic metres they fill. Water sets the reference point at exactly 1,000 kg/m³ (1 g/cm³ at 4°C, the temperature at which it is densest), which is why the unit menu offers kg/m³ and g/cm³ side by side — chemists and geologists usually read the latter, engineers the former.
The formula's shape reflects a plain physical fact: pack twice the mass into the same box and density doubles; pour the same mass into a box twice as large and density halves. That is why ice floats — its molecules lock into an open hexagonal lattice on freezing, taking up about 9% more room while carrying the same mass, so density drops from 1,000 kg/m³ to roughly 917 kg/m³. Water is one of the few common substances that is less dense as a solid than as its own liquid.
The genuine limit: this instrument returns one uniform density from one mass reading and one volume reading, so it cannot separate a composite object into its parts. A gold-plated tungsten bar reports the density of the whole lump — and tungsten, at 19,300 kg/m³, sits close enough to gold's 19,320 kg/m³ that an overall reading alone will not catch the substitution. Real materials also are not always solid throughout; a rock threaded with air pockets reads lighter than the mineral it is made of, exactly as the ratio says it should.
- Enter the object's Mass in kilograms or grams, whatever the source scale reads.
- Enter its Volume in millilitres, litres, or cubic metres — use water displacement in a measuring cylinder if the shape is irregular.
- Read the Density result in kg/m³, or switch its unit menu to g/cm³ to compare directly against a materials table.
- Check the figure against water's 1,000 kg/m³: anything below that value floats, anything above it sinks.
Worked example — 5 kg in 5 litres
Fill a container with exactly 5 litres of a liquid and set it on a scale reading 5 kg. The instrument's base unit for volume is cubic metres, so 5 litres first becomes 0.005 m³. The formula does the rest: ρ = m ⁄ V = 5 ⁄ 0.005 = 1,000 kg/m³ — not a coincidence, since five litres of water weighs almost exactly five kilograms. This example is really water measuring itself, which is why 1,000 kg/m³ is the number every other density on this instrument gets compared against.
Switch the Density field to g/cm³ and the same result reads 1.000 g/cm³ — the form chemists usually use, since it equals a sample's mass in grams divided by its volume in millilitres and matches a hydrometer or pycnometer reading with no further arithmetic needed.
Questions
What's the difference between density and specific gravity?
Specific gravity is density divided by water's density (1,000 kg/m³), so it carries no units — a specific gravity of 2.7 for granite means it is 2.7 times as dense as water. This instrument reports density directly in kg/m³ or g/cm³; to get specific gravity, take the g/cm³ reading and divide by 1, since water is defined as 1 g/cm³ at 4°C.
Why does volume need to be in cubic metres for the formula to work?
Because kg/m³ is the SI-consistent pairing: a kilogram of mass over a cubic metre of space gives density directly, with no hidden conversion factor. Enter volume in litres or millilitres instead and the instrument converts internally — 5 litres becomes 0.005 m³ — so the ratio comes out right no matter which unit you typed the reading in.
Does density change if I have more of the material?
No. Density is an intensive property — cut a block of aluminium in half and each piece still reads 2,700 kg/m³, because mass and volume shrink by the same factor and the ratio cancels. Only intensive properties such as density, pressure, and temperature stay fixed regardless of quantity; mass and volume themselves are extensive and do scale with how much material is there.
Why is ice less dense than liquid water?
Because water molecules lock into an open hexagonal lattice when they freeze, taking up about 9% more space than the same mass does as a liquid. That drops ice's density to roughly 917 kg/m³, below water's 1,000 kg/m³, so it floats with about 90% of its bulk submerged — the visible tip of an iceberg really is only a tenth of the whole.
Can this formula tell two different materials apart?
Only if their densities differ enough to matter at your instrument's precision. Gold (19,320 kg/m³) and tungsten (19,300 kg/m³) sit within about 0.1% of each other, close enough that an overall density reading alone cannot reliably separate a solid gold bar from a gold-plated tungsten one — a substitution coin forgers and bullion fraudsters have exploited for exactly this reason.
What happens if Volume is entered as zero?
The instrument blocks the calculation and asks for a volume greater than zero, because dividing mass by zero volume is undefined — infinite density has no physical meaning. A point mass or theoretical singularity cannot be represented this way; any real object, however small, occupies some nonzero extent, and that is what the formula needs.