pounds per cubic inch (lb/in3) to grams per cubic centimeter (g/cm3) conversion

What is the Pound per Cubic Inch?

The pound per cubic inch is a US customary and imperial unit of mass density, giving the number of avoirdupois pounds packed into one cubic inch. Because a cubic inch is tiny, this unit yields large numbers and is reserved for very dense materials such as metals.

Definition

One pound per cubic inch equals one avoirdupois pound (0.45359237 kg) in a volume of one cubic inch (1.6387064×10⁻⁵ m³). The result is:

$$1\ \text{lb/in}^3 = 27679.9\ \text{kg/m}^3$$

Since an inch is exactly 0.0254 m and a pound exactly 0.45359237 kg, the factor 27679.9047... kg/m³ is exact.

Origin and History

Like other Anglo-American density units, it combines the avoirdupois pound with the cubic inch, a fine-grained volume long used in machining and metalworking. It became a favored unit in metallurgy and mechanical engineering, where compact, high-density samples are measured.

Law and Notable Facts

The defining pound and inch were fixed exactly by the 1959 international yard and pound agreement. A striking fact: one pound per cubic inch is about 27.68 times the density of water, so almost every everyday liquid has a density well below 0.1 lb/in³, making the unit practical mainly for solids and metals.

Real-World Examples and Conversions

Aluminum is about 0.098 lb/in³, steel about 0.284 lb/in³, lead about 0.410 lb/in³, and gold about 0.698 lb/in³. Water is only about 0.0361 lb/in³. To convert to kilograms per cubic meter, multiply by 27679.9; to grams per cubic centimeter, multiply by 27.6799.

What is the Gram per Cubic Centimeter?

The gram per cubic centimetre is a metric unit of density widely used in chemistry, materials science, and geology because most solids and liquids have convenient single- or double-digit values in these units.

Definition

One gram per cubic centimetre is one gram of mass in a volume of one cubic centimetre. Since a cubic centimetre is one millionth of a cubic metre and a gram is one thousandth of a kilogram, the unit equals exactly 1000 kilograms per cubic metre.

$$1\ \text{g/cm}^3 = 1000\ \text{kg/m}^3$$

It is numerically identical to the gram per millilitre and to the tonne per cubic metre.

Origin and History

The unit arose from the centimetre-gram-second (CGS) system introduced in the 19th century, in which it was the standard measure of density. It was historically anchored to water: the gram was originally defined so that one cubic centimetre of water at maximum density weighed almost exactly one gram, giving water a density near 1 g/cm³.

Law and Notable Facts

Though CGS has been superseded by SI, the gram per cubic centimetre remains the everyday unit for tabulating densities of materials. A substance with density less than 1 g/cm³ floats on water while a denser one sinks. Osmium and iridium, the densest naturally occurring elements, sit around 22.6 g/cm³.

Real-World Examples and Conversions

• Water at 4 °C: about 1.000 g/cm³ (1000 kg/m³).
• Aluminium: about 2.70 g/cm³; iron: about 7.87 g/cm³.
• Gold: about 19.3 g/cm³ (19300 kg/m³).
• 1 g/cm³ = 1000 kg/m³ = 1 g/mL = 1 kg/L.