The US liquid quart is a unit of volume in the US customary system with the symbol qt.
The US liquid quart is equal to 1/4 US liquid gallons, 2 US liquid pints, 4 US liquid cups, 8 US liquid gills or 32 US fluid ounces. The SI / metric equivalent is ≈ 0.946353 L.
The US liquid quart was based on exactly 57.75 in³ which was derived from the 1959 international yard and pound agreement whereby all traditional length and volume measures were legally standardised.
The liquid gallon is a unit of volume in the US customary unit system and uses the symbol gal.
It is the most common use of the word gallon and is defined as 231 in³. It is made up of 4 quarts where there are 2 pints in a quart and 16 US fluid ounces in a US pint. There are therefore 128 US fluid ounces in a US gallon.
The term gallon is most prevalent when discussing and trading oil and fuel. To ensure consistency, the temperature of the liquid (typically petroleum or alcohol) is understood to be 15.6 °C (60 °F) at the time of measurement.