# Thread: compound interest calculation with regular deposits over different periods

1. Member
Join Date
Aug 2011
Posts
3

## compound interest calculation with regular deposits over different periods

Hi there,

I am putting together a calculator which does compound interest calculation with regular deposits over different periods.

Full html code in text format below is of working solution based upon changing all periods to weekly and calculating totals weekly. However I want to instead of doing it this way have different periods calculated only in their respected period length ie if 4 year selected than the inflated amount is only added every 4 years.

Basically I want pic 1 to look like pic 2 or excel attachment

2. Registered User
Join Date
Sep 2013
Posts
1
That's a good idea. I have seen many online calculators. It's truly helpful as we can't all be good with numbers. Several of us have struggled with math since early school days. Yet, adults need to build certain math skills if we want to make healthy financial choices. We have to know throw to calculate simple interest, as well as compound interest. Likewise, those seeking to invest have to know how to compute dividend returns.

3. To do simple interest for a year, the formula is trivial. Convert the interest from percent to decimal (e.g., 5% = 0.05) and the formula is (1 + i) * amount to be compounded. For more years compounded annually, it's Amt * (1 + i) ** years. To compound it more often than once a year, divide the interest by the number of periods and multiply years by the same amount. If you compound it monthly, divide i by 12 and replace years by months in the exponent.

In mortgage.htm, that value is calculated as x on line 75 to be used in a mortgage calculation on line 77. On line 71, the interest rate percentage is divided by 100 and 12 to make it a decimal value and determine the monthly interest rate.

HTH