Density Calculator
Density from mass and volume, or any of the three from the other two
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What this calculator computes
Density is one of the most fundamental physical properties of any material — the ratio of mass to volume, expressed in units like kg/m³, g/cm³, or lb/ft³ — and the calculator solves for any of the three variables (density, mass, or volume) given the other two. The relationship ρ = m/V is exact and applies to all matter, but the practical value depends heavily on the material: water at 4°C has a density of exactly 1000 kg/m³ (or 1 g/cm³), iron is about 7870 kg/m³, aluminium 2700 kg/m³, gasoline about 750 kg/m³ at room temperature, and air at sea level about 1.225 kg/m³. The calculator handles unit conversions internally, accepting mass in kg, g, lb, or oz, and volume in m³, L, mL, ft³, gallons, or cubic inches, with the output density expressed in any of the standard density units. Common applications include material identification (where measuring an unknown sample's density narrows the possibilities to a short list of candidates), shipping calculations (where density determines whether a load is "weight-limited" or "volume-limited" in freight pricing), buoyancy analysis (where comparing a body's density to fluid density predicts whether it will float or sink), and concentration calculations in chemistry where solute mass per unit solvent volume drives reaction stoichiometry.
Calculator
The formula
Formula
ρ = m / V
Worked example
When to use this calculator
Use this calculator any time you have two of the three values (mass, volume, density) and need the third, or any time you want to verify a material's identity by comparing measured density against published reference values. Common scenarios include shipping freight where the density-vs-volume calculation determines pricing tier, lab work where mass/volume conversions feed into concentration calculations, jewellery and precious-metal authentication where density discriminates real from counterfeit, and engineering material selection where stiffness-to-density ratios drive structural choices. The calculator assumes uniform composition and pure materials; mixtures, foams, porous solids, and composite materials need a measured density rather than a calculated one because the published density of the constituent does not predict the bulk density of the assembly.
Common input mistakes
- Mixing unit systems within a single calculation. A mass in kilograms divided by a volume in cubic feet produces a nonsensical density figure. The calculator handles unit conversion internally, but hand calculations need consistent units throughout: kg with m³, or g with cm³, or lb with ft³ — not mixed.
- Ignoring temperature effects on liquid density. Water at 4°C is exactly 1000 kg/m³, but at 20°C it is 998.2 kg/m³ and at 80°C it is 971.8 kg/m³ — a 3% difference across typical temperature ranges. Liquid-density measurements need a temperature reference; concrete chemistry and fuel-sales standards specify temperature-corrected density rather than raw measurements.
Frequently asked questions
What is the density of water?
Pure water at 4°C and standard atmospheric pressure has a density of exactly 1000 kg/m³, or equivalently 1 g/cm³. The 4°C reference is the temperature at which water reaches maximum density; at 0°C just before freezing, the density drops slightly to 999.84 kg/m³, and at 20°C room temperature it falls to 998.2 kg/m³. Salt water (seawater) is denser at about 1025 kg/m³ because dissolved salts add mass without proportionally increasing volume.
Why does temperature affect density?
Most materials expand when heated because the increased thermal energy makes molecules vibrate more vigorously, occupying more average space per molecule. The mass stays constant while the volume grows, so density falls. Liquids show the effect more strongly than solids: gasoline expands about 0.06% per degree Celsius, water expands about 0.02% per degree, while aluminium expands only about 0.007%. Density tables specify a reference temperature, typically 4°C for water and 20°C for most other liquids and solids.
What is specific gravity and how does it relate to density?
Specific gravity is the ratio of a material's density to the density of a reference material — typically water at 4°C for liquids and solids, or air at 0°C and 1 atmosphere for gases. Specific gravity is dimensionless and numerically equal to the density in g/cm³ for solids and liquids referenced to water. A material with specific gravity 7.8 (steel) has a density of 7.8 g/cm³ or 7800 kg/m³. The two terms are often used interchangeably, with specific gravity preferred in mineralogy and gemology contexts.
How does density determine whether something floats?
An object floats in a fluid if its average density is less than the fluid's density, sinks if greater, and is neutrally buoyant if equal. A wood block with density 600 kg/m³ floats in water (1000 kg/m³); an iron ball at 7800 kg/m³ sinks. Steel ships float despite the steel itself being denser than water because the average density of the ship — including the air in its interior compartments — is less than water. The same principle drives submarine ballast systems and hot-air balloon physics.
What is a typical density for common materials?
Approximate densities at room temperature: air 1.2 kg/m³, gasoline 750 kg/m³, ethanol 790 kg/m³, water 1000 kg/m³, aluminium 2700 kg/m³, iron 7870 kg/m³, copper 8960 kg/m³, lead 11,340 kg/m³, gold 19,300 kg/m³, platinum 21,450 kg/m³. The range spans more than four orders of magnitude from gases to dense metals, with most everyday solids falling in the 1000–10,000 kg/m³ band.