input() function returns a string into your variables. That is,
input() literally returns you the raw text that you typed. So when you are using those variables for calculation, you are supposed to convert the variable to the respective datatype.
For example, when you do
inches = input("Enter inches"), the
inches variable now is of type
str (string), which you can see by running
Ideally, since you are doing arithmetic calculations with the variable, you can for example convert the
inches variable to a floating point number by doing
inches = float(inches)
Or as a single step, you can do the following for your variable:
inches = float(input("Enter inches "))
Similarly handle all the variables that you read using
Hope this helps.