65682 Three PHP online calculators

We need 3 php calculators that use a simple algorithm to show how much money you will have after a certain time, if you put in a monthly or anual amount of money. Two of the calculators are already availible as excel sheets, so it should be easy for those two, the other one has to be based on a set of numbers from which it has to be calculated. Time span is max. 5 days.