Density Calculator
Density from mass and volume in metric and imperial units, with a float or sink verdict against water.
What it does
Density packs mass into volume: the same kilogram feels light as foam or heavy as lead depending on the space it fills. Engineers check it before picking hull materials, cooks meet it when oil floats on soup, and geologists read rocks by it.
The tool above takes mass with volume in metric or imperial. It returns density in both systems with the ratio against water and a plain verdict: sinks, floats, or near water density.
The default of 2 kg in 1.5 L gives 1,333.33 kg/m3 (83.24 lb/ft3), about 1.33 times water, so it sinks. Pure water itself reads 1,000 kg/m3 exactly, while ice at 917 kg/m3 floats with roughly a tenth above the surface.
Units follow the SI derived unit of kilogram per cubic meter with the US water density figures published by the Geological Survey matching the same scale. Both agree that 1 g/mL equals 1,000 kg/m3, so kitchen and lab numbers convert without friction.
How to use
- Pick metric (kg, liters) or imperial (pounds, US gallons).
- Weigh the sample alone and enter the mass.
- Measure the volume, by displacement for irregular shapes.
- Read density first, then the ratio against water.
- Use the other system line when a datasheet wants the twin unit.
Formula
- mass
- Kilograms or pounds of the sample weighed alone.
- volume
- Liters or US gallons; displacement covers odd shapes.
- 1,000 kg/m3
- Water reference: 62.43 lb/ft3 in imperial.
Imperial converts to metric first (1 lb = 0.45359237 kg, 1 US gallon = 3.78541 L), then runs one division, so both systems agree. Temperature shifts liquids slightly: warm water reads a touch below 1,000 kg/m3.
Worked example
Example: 2 kg in 1.5 L
Metric defaults: mass 2 kg, volume 1.5 L.
- Volume in cubic meters: 1.5 / 1000 = 0.0015 m3.
- Divide: 2 / 0.0015 = 1,333.33 kg/m3.
- Imperial twin: 1,333.33 / 16.01846 = 83.24 lb/ft3.
- Against water: 1,333.33 / 1,000 = 1.33x, so it sinks.
- Tool shows 1,333.33 kg/m3, 1.33x water (Sinks in water), 83.24 lb/ft3.
Reference table
| Material | Density | In water |
|---|---|---|
| Gold | 19,300.00 kg/m3 | Sinks fast |
| Aluminum | 2,700 kg/m3 | Sinks |
| Water | 1,000.00 kg/m3 | Neutral line |
| Ice | 917 kg/m3 | Floats |
| Oak wood | 750 kg/m3 | Floats |
Limits
- Single average only; layered objects need each layer weighed.
- Liquids shift with temperature and dissolved salts.
- Porous samples trap air unless soaked first.
- Hollow shapes read low because air counts as volume.
Common mistakes
- Dividing grams by liters without matching kilos to cubic meters.
- Using UK gallons (4.546 L) where the tool expects US gallons (3.78541 L).
- Weighing the container with the sample.
- Reading displacement at the meniscus top instead of the bottom.
- Calling anything above 1,000 exactly a sinker when 1.01x sits borderline.
Try it yourself
Quick checks. Answers sit tucked under each question.
1 kg of water in 1 L?
1 / 0.001 = 1,000.00 kg/m3, 1x water: near water density.
19.3 kg gold bar displacing 1 L?
19.3 / 0.001 = 19,300.00 kg/m3, 19.3x water: sinks.
Imperial defaults 4.41 lb in 0.396 gal?
About 1,334.43 kg/m3 (83.31 lb/ft3), 1.33x water: sinks.
Questions
What is the formula for density?
Mass divided by volume. In SI that is kilograms per cubic meter.
What density floats on water?
Below about 0.95x water (950 kg/m3). Ice at 917 and oak near 750 both float.
How do I measure volume of a rock?
Submerge it in a graduated container and read the displaced water. That volume pairs with the dry weight.
Why does ice float if it is water?
Ice crystals pack looser than liquid, so 917 kg/m3 sits below the 1,000 line.
kg/m3 to lb/ft3?
Divide by 16.01846. Water 1,000 kg/m3 is 62.43 lb/ft3.
Does temperature matter?
A little for liquids: warm water reads slightly below 1,000. Solids barely move.