The square foot is a unit of area and is an imperial unit with the symbol ft².
One square foot is equal in area to a square with edges one foot in length.
It is used a lot in expressing the internal size of a house, apartment, office or other properties so is a useful unit to understand.
The square inch is a unit of area and is an imperial unit with the symbol in².
One square inch is equal in area to a square with edges one inch in length.
The square inch is a common unit of measurement in the UK and US.