Simplify the following text for a Grade 4 native English-speaking person.
Original: It is defined as the volume of a cube with sides of one foot ( 0.3048 m ) in length . A standard cubic foot ( abbreviated scf ) is a measure of quantity of gas , sometimes but not always defined as a cubic foot of volume at 60 degrees Fahrenheit and 14.7 pounds per square inch ( PSI ) of pressure .
Simplified: A cubic foot is a measure of volume .