Density tells you how much matter is packed into a given space, and it is one of the quickest ways to identify a material, predict whether something will float, or turn a volume into a weight. This calculator solves ρ = m/V for density, mass or volume, accepts kitchen, lab and engineering units, and adds the specific gravity, a float-or-sink verdict for fresh water and the closest match from a built-in list of common materials.
How to use the density calculator
- Under Solve for, choose Density, Mass or Volume.
- Enter the Mass (m) in kg, g, mg, metric tons, lb, oz, US tons or stone.
- Enter the Volume (V) in m³, L, mL, cm³, ft³, in³, US gallons, yd³, cups, fluid ounces or quarts.
- When solving for mass or volume, enter the Density (ρ) in kg/m³, g/cm³, g/mL, kg/L, lb/ft³, lb/in³ or lb/gal.
- Choose the unit of the answer under Show the result in, then read the conversions, the specific gravity, whether the object floats or sinks in fresh water (with the share below the waterline for floaters) and the closest common material.
Density formula
Rearranged for the other two unknowns:
Specific gravity compares a density with water’s:
Mass, volume and density must all be greater than zero. A computed density above 1,000,000 kg/m³ is rejected as a likely unit mix-up, since the densest element, osmium, is only about 22,590 kg/m³.
Unit equivalences
| Unit | Equal to 1 g/cm³ |
|---|---|
| g/mL, kg/L | 1 |
| kg/m³ | 1,000 |
| lb/ft³ | 62.43 |
| lb/US gal | 8.345 |
| lb/in³ | 0.03613 |
Worked examples
500 g in 400 cm³ (the default)
ρ = 500 g ÷ 400 cm³ = 1.25 g/cm³ = 1,250 kg/m³ = 78.04 lb/ft³ = 10.43 lb/gal
Specific gravity is 1.25, so the object sinks in fresh water. That density is close to glycerol's, about 1.26 g/cm³.
Mass from volume. Solve for mass with 1 g/cm³ and 1 gal, and show the result in pounds: a US gallon of water weighs about 8.345 lb (3.785 kg).
Volume from mass. A 1 kg gold bar at 19.3 g/cm³ occupies only 51.8 cm³, a cube about 3.7 cm on each side.
Measuring volume by water displacement
For a lump, a stone or a piece of jewelry, measuring volume with a ruler is hopeless. The fix is the one credited to Archimedes: submerge the object and measure the water it pushes aside.
- Weigh the object on a kitchen or lab scale.
- Half-fill a graduated cylinder or measuring jug and note the level.
- Lower the object in completely, knocking off air bubbles, and note the new level.
- The difference is the volume, because 1 mL equals 1 cm³.
Suppose a 412 g rock raises the water from 250 mL to 400 mL. Enter 412 g and 150 mL: the density is 2.747 g/cm³, and the calculator’s closest match is granite. Small objects need a narrow cylinder, since a 0.5 mL misreading on a ring-sized volume can throw the result off by tens of percent.
Densities of common materials
Approximate values near room temperature, taken from the calculator’s built-in list:
| Material | kg/m³ | g/cm³ | lb/ft³ |
|---|---|---|---|
| Air (20 °C, sea level) | 1.204 | 0.0012 | 0.075 |
| Cork | 240 | 0.24 | 15.0 |
| Pine wood | 500 | 0.50 | 31.2 |
| Gasoline | 740 | 0.74 | 46.2 |
| Ice | 917 | 0.917 | 57.2 |
| Fresh water | 998 | 0.998 | 62.3 |
| Seawater | 1,025 | 1.025 | 64.0 |
| Concrete | 2,400 | 2.40 | 149.8 |
| Aluminum | 2,700 | 2.70 | 168.6 |
| Steel | 7,850 | 7.85 | 490.1 |
| Copper | 8,960 | 8.96 | 559.4 |
| Lead | 11,340 | 11.34 | 707.9 |
| Mercury | 13,534 | 13.53 | 844.9 |
| Gold | 19,300 | 19.30 | 1,204.9 |
Wood, concrete and gasoline vary noticeably by species, mix and blend. Liquids also change with temperature: water peaks at about 999.97 kg/m³ near 4 °C and drops to about 958 kg/m³ at its boiling point. Gas densities depend strongly on pressure and temperature, so work those out with the ideal gas law calculator. To switch between density units without a mass or volume, use the density converter.
Frequently asked questions
What is the formula for density?
Density is mass divided by volume: ρ = m ÷ V. An object of 500 g that takes up 400 cm³ has a density of 1.25 g/cm³, which is 1,250 kg/m³.
How do I convert g/cm³ to kg/m³ and lb/ft³?
Multiply by 1,000 for kg/m³ and by about 62.43 for lb/ft³. So 1 g/cm³ equals 1 g/mL, 1 kg/L, 1,000 kg/m³, 62.43 lb/ft³ and 8.345 lb per US gallon.
What is specific gravity?
Specific gravity is density divided by the density of water, so it has no units. The calculator uses 1,000 kg/m³ for water. Anything with a specific gravity below 1 floats in fresh water, and the specific gravity tells you what fraction of a floating object sits below the waterline.
How do I find the volume of an irregular object?
Use water displacement. Lower the object into a graduated container and read how much the water level rises; that rise is its volume, since 1 mL equals 1 cm³. Divide the object's mass by that volume to get its density.
Why is ice less dense than water?
When water freezes, its molecules lock into an open hexagonal lattice that takes up about 9% more room. Ice at about 917 kg/m³ therefore floats, with roughly 92% of its volume below the surface in fresh water and about 89% in seawater.