Hi,

I want to calculate expenses over a period of times.

My inputs are :
- Initial Expense (P[0])
- Number of month (n)

Currently I do not take inflation into acount so my formula is just:

Total Expense : S[n] = P[0]*n

Now, if I want to take inflation into account, my expenses would
increase for each period.
So I have one more input : R is the monthly inflation rate.

So the expense each month is : P[i]=P[i-1]*(1+R)=P[0]*(1+R)^i

An my total expense is S[n] = Sum(P[i],i=0..n) = P[0]*Sum((1+R)^i,
i=0..n)

How do I translate this in a Excel formula ?

Thank you