To convert square feet to cubic feet, you're going to need to do some measuring. The formula for a square or rectangular object's cubic feet is its length times width times height, or L x W x H. You might use this formula to figure out how many cubic feet of soil to buy for your garden, for example, or to determine how many ounces of pesticide to use when releasing a bug bomb inside a room of your house.
Measure the object's height in feet. (You have already measured the object's length and width to get its measurement in square feet.)
Divide that number by 12 to get its measurement in feet, if you measured the object in inches. If the object is 6 inches tall, it is 0.5 feet.
Multiply the object's height in feet by its square foot measurement to convert from square feet to cubic feet.
This formula works only for square or rectangular objects.