pounds per cubic foot (lb/ft3) to grams per cubic centimeter (g/cm3) conversion

What is the Pound per Cubic Foot?

The pound per cubic foot is an imperial and US customary unit of mass density, stating how many avoirdupois pounds of mass fill one cubic foot of volume. It is standard in North American construction, HVAC, and materials engineering.

Definition

One pound per cubic foot equals one avoirdupois pound of mass (0.45359237 kg) distributed through one cubic foot (0.028316846592 m³). Dividing gives:

$$1\ \text{lb/ft}^3 = 16.0185\ \text{kg/m}^3$$

The relation derives exactly from the defined pound and foot, so the conversion factor 16.018463... kg/m³ is fixed.

Origin and History

The unit grew out of English commercial weights and measures, combining the avoirdupois pound (standardized over centuries and fixed internationally in 1959) with the cubic foot. It persisted in engineering after the US and UK adopted the international pound, remaining entrenched in building codes and product data sheets.

Law and Notable Facts

Under the 1959 international yard and pound agreement, the pound is exactly 0.45359237 kg and the foot exactly 0.3048 m, making lb/ft³ exactly convertible. A useful benchmark: liquid water is about 62.4 lb/ft³, a number engineers memorize for buoyancy and hydrostatic calculations.

Real-World Examples and Conversions

Air at sea level is about 0.075 lb/ft³. Dry softwood lumber runs roughly 25–35 lb/ft³, while concrete is about 150 lb/ft³ and steel about 490 lb/ft³. To convert to kilograms per cubic meter, multiply by 16.0185; to grams per cubic centimeter, divide by 62.43.

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.