calculating compound interest

[cliff]

Hi, I would like to calculate maturity value of the following investments and
interest
yearwise interest

deposit_name cdate amount period rate no. of
autorenewals
rap90 1/4/09 10000 90 days 9
3
rap90 1/3/09 10000 90 days 9
3
qirp 1/5/08 10000 36 months 12
-
qirp 1/8/08 10000 24 months 12
-
rap30 15/6/08 10000 30 days 6
11
rap30 10/4/09 10000 30 days 6
11


for rap90 deposit I want to calculate interest earned after 360 days ie.,
90+ 90*3 autorenewals. similarly rap30 deposit earned after 360 days
ie., 30 +30*11 autorenewals. I earn quarterly compounded interest on my
qirp deposits,so compound interest on qirp on maturity date.

please help to solve this


thanks

cliffs

 

[KenSheridan via AccessMonster.com]

I'd have thought Excel would be the first choice for this, but it can be done
in Access of course.

The sum to which the principle will grow with interest compounded is given by
the formula:

S = P(1+ i)^n

where P is the principal, i is the periodic interest and n is the number of
periods. So taking rap90 as an example, at 9 percent per annum compounded at
90 days over 360 days this would be:

10000 *((1 + (9/(365/90)/100)) ^ (360/90))

which is 10917.66

Similarly for your 3 year qirp deposit at 12 percent per annum compounded
quarterly:

10000 *((1 + (12/(12/3)/100)) ^ (36/3))

which is 14257.61

The above equate to an expression in Access such as:

amount * ((1 + (rate/(yearlength/period)/100)) ^ (term/period)

I should point out, however, that in the dummy data you've provided your
period column confuses two different attributes. For the rap accounts the
length of the period at which interest is compounded is correctly given, but
for the qirp accounts you have given the length of the term in this column;
as interest is compounded quarterly with these accounts the period should be
3 and the year 12. The use of different units for the year
lengths/periods/terms (365/90/360 days for the rap account and 12/3/36 months
for the qirp account in the above examples) is fine so long as the same units
are used consistently within each account.

The above does assume that the interest rates are quoted over a calendar year
of 12 months or 365 days, which might not necessarily be the case.

Ken Sheridan
Stafford, England