Originally Posted by

**jonah** The problem, as noted by mathceleb, is your payments are monthly but your interest compounding is continuous. I could be wrong but I believe this type of situation falls under the category of complex (or general annuity).

Accordingly, a continuously compounded rate of 8% is equivalent to a nominal rate of approximately 8.026726025% compounded monthly since both have an effective nominal rate of approximately 8.328706767%.

Thus, with {j = 8.026726025%, m = 12}, and since i = j/m, you simply plug the resulting value of i into the formula quoted by lllll. At the end of 8 years, their savings account should be worth about $13,402.44 if the monthly deposits were made at the end of each month. If the deposits were made at the beginning of each month, their savings account should be worth about $13,492.09 since you’d have to use the annuity due version of the future value annuity formula.