Re: calculate interest for one-time payment on loan

[John Machin <sjmachin lexicon net>]

On 9/02/2007 3:37 AM, ken wrote:
> Hi, people,
>
> This should be a simple thing to do.  I'm surprised there's not a
> function for it.  Or maybe there is one.  I've looked at the FAQ, read
> through quite a few of the functions, and searched the archives for this
> list and haven't found what I need.  As my Subject line says, I'm
> looking for a way to calculate interest for one-time payment on loan.
> Too simplistically, it's this:
>
> InterestAmt = DailyInterestRate * NumberOfDays
>
> DailyInterestRate = AnnualInterestRate / 365
>
> NumberOfDays(DateStart, DateEnd)
>
> Gnumeric is nice because variables such as the above can be hardcoded
> into a formula or fetched from a cell.

Gnumeric is nice in many respects, but AFAIK that functionality is, and 
always has been, fundamental to *all* spreadsheet software :-)

>  I could hardcode everything but
> DateEnd; that needs to be fetched from a cell.
>
> Anyone know a way to do this?

Perhaps I'm missing something, but I would have been highly surprised if 
there were a function supplied for such a short uncomplicated formula.

Assuming:
1. your DateEnd value is in cell A1
2. the start date is 31 December 2006
3. the annual interest rate is 7%
then the formula for "interest amount" is
 7 / 100 / 365 * (A1 - DATE(2006, 12, 31))
(or something like that) -- isn't it?

HTH,
John