1. The problem statement, all variables and given/known data What is the formula for compounded annual contributions which increase at a fixed % rate, yet where the principal interest rate is 0%. IOW the classic "money under the mattress" savings where the yearly contributed amount increases at a fixed %. E.g, year one contribution is $1,000, each year the contributed amount increases by x%, but with zero % interest on the principal. How much total saved after n years? 2. Relevant equations All the equations I can find assume compounded principal and fixed annual contributions. What I want is the opposite - non-compounded principal and annual contributions which increase at a fixed % each year.