Finding the area of an object is a very fundamental task in many designs.
Area is found by multiplying the length by the width: A = L x W
For this to be useful the units must be known. If measuring lengths in inches, then the area is calculated in inches squared.
To convert to feet squared, remember there are 12" per foot. So one square foot has 12 x 12 inches or 144 square inches.
Example: how many square feet in 210 inches squared?
Answer: 210 in squared / 144 = 1.458 feet squared
Likewise the volume is used in many design problems. For example finding bouyancy or weight of a solid or how much something can hold.
Volume is found by taking L x H x W: V = L x H x W. (The order doesn't matter)
As in area, the units must be consistent. if you measure length in inches then volume will be in cubic inches.
To convert to cubic feet, remember there are 12 inches per foot, so 12 x 12 x 12 = 1728 in cubed.
So one cubic foot is equal to 1728 in cubed.
Example: You are told a box holds 2.8 cubic feet. How many inches cubed are in the box?
Answer: 2.8 ft3 x 1728 in3/ft3= 4838.4 in cubed.
It is super important to know and understand the units you are using and how to convert into other units.