The formula
How to calculate density
Density is mass per unit volume — how much matter is packed into a given space. It determines whether something floats, and it is one of the simplest ways to identify an unknown material.
Specific gravity is density relative to water, so it has no units and is the same number in any measurement system. Anything with a specific gravity below 1 floats in water.
What to enter:
- Mass (g)
- Volume (cm³)
No submit button: type and the answer moves. Your inputs end up in the link, so the page can be shared already filled in.
The calculation runs on exactly the numbers currently in the fields above, recomputed in full each time — there is no dependency on the order values are entered in, so adjusting one input to test a scenario and then changing it back leaves the result exactly where it started.
Why density matters
This kind of calculation comes up in coursework, in a laboratory or field setting, and in professional practice, and the arithmetic is identical in every case — only the numbers being fed into it, and what is riding on getting them right, actually change.
It is useful for checking a manual calculation before submitting or acting on it, and equally useful for building intuition about a formula by adjusting one input at a time and watching how the result moves in response — a much faster way to understand a relationship than working through several versions of the algebra by hand.
It is worth remembering that a formula is only ever as good as the assumptions built into it, and most of the standard equations used across science and statistics carry at least one simplifying assumption — a linear approximation, an idealised gas, a normally distributed error term — that holds well in most ordinary cases and breaks down at the extremes. The result here reflects the standard formula exactly; whether that formula's assumptions are appropriate for your particular situation is a separate judgement worth making deliberately rather than assuming automatically.
It is worth keeping a note of which inputs were used to produce a given result, particularly where the figure is going into a report or a further calculation — reproducing a result later, or explaining how it was reached, is far easier with the original inputs to hand than by trying to reverse-engineer them from the output alone.
Worked example
A concrete run-through, using the values already in the fields:
- Mass: 250 g
- Volume: 92.6 cm³
That gives:
- Density: 2.6998 g/cm³
- In kg/m³: 2,699.784 kg/m³
- Specific gravity: 2.7052
The figures above are the calculator's own default values, shown purely so the working is visible rather than hidden — the same steps apply exactly to your own numbers, entered in the fields at the top of this page.
Reading the result
Common values in g/cm³: cork 0.24, ice 0.92, water 1.00, aluminium 2.70, steel 7.85, lead 11.34, gold 19.32. The default figures here give roughly the density of aluminium.
Where this goes wrong. Density varies with temperature, and for gases with pressure as well. Water is densest at 4 °C, which is why ice floats and lakes freeze from the top down.
A result that is wrong by an exact factor of ten, a hundred or a similar round number is almost always a units error rather than a mistake in the formula itself — checking each input against the unit stated beside it is the fastest way to track it down.
By displacement: submerge it in water and measure the volume of water displaced. Archimedes' method still works and needs no equipment beyond a measuring cylinder.
Specific gravity is density divided by the density of water, which makes it dimensionless. The numerical value in g/cm³ is almost identical, which is why the two are often conflated.
The answer it gives you is density. With 250 g mass and 92.6 cm³ volume, that comes to 2.6998 g/cm³. Change any field and the figure moves with it.
Generally, no more than the least precise input justifies — a result reported to six decimal places from inputs measured to two significant figures is implying a precision the calculation does not actually have. The calculator shows full precision so you can round appropriately for your own use.
Yes — the equation shown in the formula section above is the standard form used in textbooks and reference material for this calculation, not a simplified or approximate version.
Yes, in the sense that it applies the correct standard formula and returns an accurate result for the inputs given — but check your own course or publication's requirements for how results should be rounded, presented and referenced, since those conventions vary and are not something a calculator can know on your behalf.