Density calculator
Density = mass ÷ volume, in metric or US units, with the conversions shown
Choose what to find and fill in the other two. The example is 500 g in 250 cm³.
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- In kg/m³
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- In g/cm³
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- In lb/ft³
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- In fresh water it would
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Working, step by step
The density formula
Density is how much mass is packed into each unit of volume: density = mass ÷ volume, written ρ = m/V. The same formula rearranges to mass = density × volume and volume = mass ÷ density. For example, 500 g in 250 cm³ is 500 ÷ 250 = 2 g/cm³.
Units
The page turns every mass into kilograms and every volume into cubic meters first, does the sum, then turns the answer into the unit you chose. Each conversion is listed in the working so you can check it. The factors are exact by definition: 1 pound is 0.45359237 kg, 1 inch is 2.54 cm, and a US gallon is 231 cubic inches. 1 g/cm³ is the same as 1 g/mL, 1 kg/L and 1,000 kg/m³.
Will it float?
Pure water has a density of about 1 g/cm³ (1,000 kg/m³; 999.97 at 4 °C and about 997 at 25 °C). A solid object denser than the liquid sinks and a less dense one floats, so the result card compares your answer with fresh water. Seawater is a little denser, about 1.025 g/cm³, which is why floating is easier in the sea.
Tips
- For an odd shape, find the volume by dropping it into a measuring jug of water and reading how far the level rises.
- Density depends on temperature, especially for gases and liquids, so tables quote it at a stated temperature.
- US fluid ounces and gallons are used here; UK (imperial) gallons are about 20% bigger.
Formula and sources
- Exact conversion factors: NIST Handbook 44, Appendix C (General Tables of Units of Measurement), and NIST Special Publication 811: 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 US gallon = 231 in³.
- Water density near 4 °C (999.97 kg/m³) and 25 °C (997.0 kg/m³): CRC Handbook of Chemistry and Physics, density of water table.
- Checked in test_maths.js: 500 g in 250 cm³ = 2 g/cm³ = 2,000 kg/m³; 1 g/cm³ = 62.42796… lb/ft³; mass of 2 L at 1 kg/L = 2 kg; 1 lb at 1 g/cm³ fills 453.59237 cm³.