pounds per cubic inch (lb/in3) to ounces per US gallon (oz/gal) 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 Ounce per US Gallon?

The ounce per US gallon is a unit of density expressing the mass in avoirdupois ounces contained in one US liquid gallon. It appears in everyday US contexts such as mixing ratios, water treatment, and beverage or fuel formulations.

Definition

One ounce per US gallon equals the mass of one avoirdupois ounce (28.349523125 g) divided by the volume of one US liquid gallon (3.785411784 L).

$$1\ \text{oz/gal} = 7.48915\ \text{kg/m}^3$$

Here the ounce is the avoirdupois ounce of mass and the gallon is the US liquid gallon (exactly 3.785411784 L, or 231 cubic inches). Using the imperial gallon (4.54609 L) instead gives a different value of about 6.236 kg/m³, so the gallon variant must always be specified.

Origin and History

The US gallon descends from the English wine gallon of 231 cubic inches, retained by the United States after Britain adopted the larger imperial gallon in 1824. Pairing it with the avoirdupois ounce created a practical density and dosing unit for American trade and agriculture.

Law and Notable Facts

This is a derived unit fixed by the exact definitions of the avoirdupois ounce and the US liquid gallon. It is especially common in dosing and concentration work, where an "ounces per gallon" rate is easy to measure and mix by hand.

Real-World Examples and Conversions

• Water (about 1000 kg/m³) corresponds to roughly 133.5 oz/gal.
• A concentration of 1 oz/gal is about 7.489 kg/m³, or 7.489 g/L.
• 8 oz/gal (a half pound per gallon) equals about 59.9 kg/m³.
• 16 oz/gal (one pound per gallon) equals about 119.8 kg/m³.