Calculating interest

[Quinny]

The initial message was deleted from this topic on 17 October 2011 at 19:44

[mindgam3]

Something like this?

Balance(n) = P(1 + r)n + c[((1 + r)n + 1 - (1 + r))/r]

When n is number of payment periods
P is initial investment
c is periodic investment

GOt it from a website, but it seems to ring some bells from college days...

[plasticpig]

=FV(5%/12,50,-100,0,1)

The first argument gets you the intrest rate per month.
The second argument is the number of months/periods.
The third argument is the amount you are saving (negative because you are receiving money).
The Fourh argument is the balance of the account when the calculation starts.
The Fith argument is wether the deposit is at the start or end of the period. 0 = End of period 1 = start of period.

[marandlau]

have something similar for my finances spreadsheet. As well as a summary page, i have a couple of loans which i have broken down into monthly statements, so i can see at each month, exactly how mych i owe, and if i increase the payment for that month, what effect it has on the final payments.

Basically; colomn A has the months down the side.
B1 has the monthly repayment
B2 has the interest rate, roughly a 5% would be a cell value of 1.005
b3 has the initial loan amount
b4 =(b3-$b$1)*$b$2

select cell b4, select all cells down to the month you want, edit, fill down.
now you can go into each cell and edit the monthly payments by replacing the $b$1 in the formula for a value. Rest of the sheet wil update automatically based on that.

for savings, change the - to a +