Divide by 0 error

[snippsat]

I might need to tell the program to treat the input as a number?

Yes,that's the first step.
So if input is a or 1.0,get a error.

>>> input_capacity = int(input("Enter the number of gallons or liters used: "))
Enter the number of gallons or liters used: a

Error:
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: 'a'
invalid literal for int() with base 10: 'a'

This ValueError can be catch and give a more useful message to user.

def capacity_prompt():
   while True:
       try:
           input_capacity = int(input("Enter the number of gallons or liters used: "))
           return input_capacity
       except ValueError:
           print('Only number as input,try again')

print(capacity_prompt())

If you run it,you see that it will only return out integer.
You use the same method with divide by zero error.

>>> 7 / 0

Error:
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero
division by zero