Density Converter

Q: Is density the same as specific gravity?

Not quite. Specific gravity relative density is the density divided by the density of water, so it has no unit. Because water is close to 1 g/cm³, a density in g/cm³ is almost the same number as the specific gravity.

Density Converter

Convert density between kg/m³, g/cm³, g/mL, kg/L, lb/ft³, lb/in³ and lb/gal, with exact factors, formulas and reference densities of common materials.

Value

From

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Formula:

Significant figures

≈ means the result was rounded to the chosen number of significant figures.

1 g/cm³ = 1 g/mL = 1 kg/L = 1,000 kg/m³ exactly. Reference values are typical at 20 °C and normal pressure; real materials vary with temperature, grade and composition.

{value} in every unit

Unit	Result

Quick conversion table: {from} to {to}

From	To

Common values

Reference	Value	Result

Unit definitions

Unit

How to use the density converter

Type a density in Value. Decimals work with a point or a comma (0.789 or 0,789).
Pick the unit you start from in From and the unit you want in To. Metric units are listed first, then US and imperial units.
The result appears as you type. Formula shows the factor for the selected pair and the line below applies it to your number.
Press Swap units (⇄) to convert the other way, change Significant figures for more or fewer digits, and use Copy to copy a line such as “1,000 kg/m³ ≈ 62.427961 lb/ft³”.

Below the result, the tool lists your value in every unit, a quick conversion table for the selected pair, reference densities of everyday materials expressed in your target unit, and the definition of each unit in kg/m³.

What density means

Density (or mass density, symbol ρ) is mass divided by volume: ρ = m ÷ V. The SI unit is the kilogram per cubic metre (kg/m³). A value tells you how many kilograms one cubic metre of the material would weigh, so 1 m³ of water at 20 °C weighs about 998 kg, and 1 m³ of steel about 7,850 kg.

Several metric units have exactly the same size, which surprises many people:

1 g/cm³ = 1 g/mL = 1 kg/L = 1 t/m³ = 1,000 kg/m³
1 g/L = 1 kg/m³

This is why chemistry tables in g/cm³ and engineering tables in kg/m³ differ only by a factor of 1,000.

US and imperial units

The pound-based units are derived from the exact definitions 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 US gallon = 3.785411784 L and 1 imperial gallon = 4.54609 L:

1 lb/ft³ = 16.018463 kg/m³ (used for soils, timber, insulation and concrete in the US)
1 lb/in³ = 27,679.905 kg/m³ = 27.68 g/cm³ (metals, plastics)
1 lb/gal (US) = 119.826427 kg/m³ (fuels, drilling mud, paints)
1 lb/gal (UK) = 99.776373 kg/m³

A handy check: water weighs about 62.3 lb/ft³ and 8.33 lb per US gallon.

Reference densities

The Common values table uses typical values at 20 °C and normal atmospheric pressure. Pure substances come from the CRC Handbook of Chemistry and Physics: water 998.21 kg/m³ at 20 °C (999.97 at 4 °C), ethanol 789.3, mercury 13,546, ice at 0 °C 916.7, aluminium 2,700, copper 8,960, lead 11,340 and gold 19,300 kg/m³. Dry air (1.204 kg/m³) follows from the ideal gas law at 20 °C and 101.325 kPa. Petrol (about 720–775, EN 228), seawater (about 1,025), concrete (about 2,400) and carbon steel (about 7,850) are typical values: the real figure depends on the blend, the salinity or the mix.

Frequently asked questions

Is density the same as specific gravity?

Not quite. Specific gravity (relative density) is the density divided by the density of water, so it has no unit. Because water is close to 1 g/cm³, a density in g/cm³ is almost the same number as the specific gravity.

Why does water not have a density of exactly 1,000 kg/m³?

The kilogram was once defined from water, but only at its densest point, about 4 °C. At room temperature water expands slightly, to about 998 kg/m³, and hot water at 90 °C is near 965 kg/m³.

How do I find a mass from a density?

Multiply the density by the volume in matching units. For example, 2.5 L of olive oil at about 0.91 kg/L weighs 2.5 × 0.91 ≈ 2.3 kg.

Why is a negative value flagged?

Density cannot be negative. The tool still shows the arithmetic but adds a warning so a sign error does not go unnoticed.

Are the reference values exact?

No. They are typical values for identification and estimates. For engineering work, use the density given by the supplier or measured at your actual temperature.