grams per cubic centimeter (g/cm3) to pounds per US gallon (lb/gal) conversion

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Though CGS has been superseded by SI, the gram per cubic centimetre remains the everyday unit for tabulating densities of materials.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.

What is the Pound per US Gallon?

The pound per US gallon is a US customary unit of mass density, giving the number of avoirdupois pounds contained in one US liquid gallon. It is widely used for fuels, paints, chemicals, and other liquids sold by the gallon in the United States.

Definition

One pound per US gallon equals one avoirdupois pound (0.45359237 kg) in one US liquid gallon (231 cubic inches, or 3.785411784×10⁻³ m³). The result is:

$$1\ \text{lb/gal} = 119.826\ \text{kg/m}^3$$

This uses the US gallon; the imperial (UK) gallon is larger (4.54609 L), so 1 lb per imperial gallon equals about 99.776 kg/m³. Values here refer specifically to the US gallon.

Origin and History

The US gallon descends from the English wine gallon of 231 cubic inches, retained by the United States after Britain redefined its gallon in 1824. Combined with the avoirdupois pound, pounds per US gallon became the standard density and shipping-weight measure for American liquid commerce.

Law and Notable Facts

The US gallon is defined as exactly 231 cubic inches and the pound as exactly 0.45359237 kg, making the conversion exact. A key fact: water weighs about 8.34 lb/gal, the basis of the water-treatment industry's "pounds per million gallons" dosing calculations.

Real-World Examples and Conversions

Water is about 8.34 lb/gal, gasoline roughly 6.0–6.3 lb/gal, and diesel about 7.1 lb/gal. Milk is around 8.6 lb/gal. To convert to kilograms per cubic meter, multiply by 119.826; to kilograms per liter, multiply by 0.119826.