Density Calculator

Density problems show up in physics homework, materials science, cooking conversions, and shipping calculations — and they always involve dividing one unit by another in ways that go wrong.

Enter mass and volume in any common units (g, kg, lb, oz; mL, L, cm³, in³, gallon) and the calculator returns density in g/cm³ (the SI-friendly default) plus equivalents in kg/m³ and lb/ft³. Or enter density and one of mass/volume to solve for the other.

Reference densities for common materials are included so you can check your numbers — water is 1.000 g/cm³ at 4°C, gold is about 19.3, balsa wood is around 0.16, mercury is 13.5. If your computed density is more than 22 (osmium territory) or negative, you've probably mixed up units somewhere.

Density is just mass divided by volume, but the unit zoo makes it confusing. SI uses kg/m³, which gives water a density of 1000 — fine for engineering but awkward for everyday use. g/cm³ gives water 1.000 cleanly. lb/ft³ gives water about 62.4. lb/in³ gives water about 0.036. All these numbers describe the same physical reality. The calculator converts between them so you can match whatever your textbook, datasheet, or building code uses.

The pain this addresses: applied density problems pull from inconsistent unit systems. A shipping calculation uses lb/ft³ for cargo density. A chemistry experiment reports densities in g/mL. A geological survey uses kg/m³. A cooking conversion needs density to translate between mass (grams) and volume (cups). Without a converter, you're toggling between mental conversions you barely remember. With one, the question reduces to 'mass and volume of what?' and the answer comes out in whatever units you actually need.

Worked example: you want to ship 20 cubic feet of crushed glass. Crushed glass density is about 1500 kg/m³ (bulk density, accounting for void space). Convert to lb/ft³: 1500 × 0.0624 ≈ 93.6 lb/ft³. Total weight: 20 × 93.6 = 1,872 lb. The shipping rate likely uses dimensional weight or actual weight, whichever is greater. Knowing the actual weight matters for freight class and quoting. The math is trivial; doing it in your head is error-prone, especially when the wrong number means you misquote a shipment by hundreds of dollars.

Where density is more subtle than the formula suggests: bulk density vs true density. A pile of sand has air gaps. The 'true' density (grain density) of silica sand is about 2.65 g/cm³, but a pile of dry sand has a bulk density around 1.6 g/cm³ because of void space. For engineering applications, you usually want bulk density. For materials science, true density. The reference table in the tool flags this for materials where the distinction matters — concrete, sand, gravel, powders. Liquids and solid metals have only one density (no voids), so the distinction doesn't apply.