There is no definitive answer to this question as the size of ladder you will need will depend on a number of factors, such as the height of your house, the width of your staircase, and your own personal preferences. However, as a general guide, most people will require a ladder that is at least 20 feet tall in order to safely reach the second story of their home. If you are unsure about what size ladder to purchase, it is always best to err on the side of caution and choose a taller ladder rather than a shorter one. This will help to ensure that you can safely and easily reach the second story of your home without any issues.