Density Calculator
Solve ρ = m ÷ V for density, mass or volume.
What is Density?
Density is mass per unit volume: how much matter is packed into a given space. It is what explains whether something floats, and it is a good way to sanity-check a measurement, because most everyday materials sit in a familiar band — water is 1000 kg/m³ (1 g/cm³), a human body about 985, steel 7850.
How it works
ρ = m ÷ V, rearranged for whichever field is blank. Masses in kilograms, grams or pounds and volumes in cubic metres, litres, millilitres or cubic feet are converted to the base pair first, and the answer can be read in whatever density unit you prefer. Because g/cm³ and g/mL are numerically identical, both are offered.
- Enter what you know. Every field recalculates as you type — there is no submit button. Leave the quantity you want blank and the page solves for it.
- Read the answer and the working. The result appears above the fold; underneath it is the formula with your numbers substituted, so the arithmetic can be checked rather than trusted.
- Check the units and the size. Units are shown on every value and selectable per field, so a result in kJ, kPa or km/h is converted rather than assumed. Sanity-check the magnitude against a known landmark such as 1 g/cm³ for water.
Examples
A textbook problem with a known answer
Every tool here is checked against standard example problems — the molar mass of C6H12O6 is 180.16 g/mol, and free fall from 20 m takes about 2.02 s at g = 9.8 m/s².
A result you want to reason backwards from
Leave the quantity you already know blank instead: given the final answer, most tools recover the starting value — the mass needed for a target concentration, or the height a fall must have had.
Common mistakes
Forgetting that a formula is only as good as its subscripts
H2O and H2O2 are different compounds. The formula field shows its parse — element by element — so a mis-typed subscript is visible before it reaches the arithmetic.
Mixing units in the middle of a calculation
The most common source of a wrong answer is a value in grams next to a formula expecting kilograms, or Celsius next to a gas constant expecting kelvin. This category converts on the way in and labels what it used.
Frequently asked questions
Why is water's density 1 g/cm³ and 1000 kg/m³?
They are the same density in different units. A cubic metre holds a million cubic centimetres, so the number scales by a thousand. Both options are selectable here.
Does density change with temperature?
Yes. Most substances expand when heated, so their density falls. Water is unusual in being densest at about 4 °C, which is why ice floats.
How do I find the volume of an irregular object?
By displacement — measure the water level before and after submerging it, and the rise is the volume. Then enter that volume with the measured mass here.