[RESOLVED] Calculate Interest?

Greetings all,

I'm trying to get this to work properly, its to calculate profit and new account balance as u put the money in a bank for interest.

For example, if we have a balance of $1000 in our account and we wish to know how much we will have in the account after 3 months using an annual interest rate of 4.5% compounded monthly:

After first month: interest earned = $1000 * 4.5 / 100 / 12 = $3.75
new balance = $1000 + $3.75 = $1003.75
After second month: interest earned = $1003.75 * 4.5 / 100 / 12 = $3.76
new balance = $1003.75 + $3.76 = $1007.51
After third month: interest earned = $1007.51 * 4.5 / 100 / 12 = $3.78
new balance = $1007.51 + $3.78 = $1011.29
So, after 3 months we will have $1011.29 in our account and we will have earned $11.29.


My code is:

VB Code:

Private Sub cmdCalculate_Click()
 
    'Proform calculations
    txtProfit.Text = Val(txtAccountbalance.Text) * 4.5 / 100 / Val(txtDuration.Text)
    txtNewbalance.Text = Val(txtProfit.Text) + Val(txtAccountbalance.Text)
    
    'To correct values to 2 decimal places since it is money.
    txtNewbalance.Text = Format(txtNewbalance.Text, "currency")
    txtProfit.Text = Format(txtProfit.Text, "currency")
    
End Sub

it doesnt work really well.. could someone tell me wad code to write?

My screenshot is attached below:
http://img104.imageshack.us/img104/7...lculatenc1.jpg

Try this:

VB Code:

Private Sub cmdCalculate_Click()
txtNewBalance.Text = txtAccountBalance.Text
txtProfit.Text = 0
For i = 1 To Val(txtDuration.Text)
    txtNewBalance = Val(txtNewBalance) + (Val(txtNewBalance.Text) * 4.5 / 100 / 12)
Next
txtNewBalance = Format(txtNewBalance.Text, "currency")
txtProfit = Format(txtNewBalance - txtAccountBalance.Text, "currency")
End Sub

whats i? it says variable not defined..

how to make it loop like wad it says?

After first month: interest earned = $1000 * 4.5 / 100 / 12 = $3.75
new balance = $1000 + $3.75 = $1003.75
After second month: interest earned = $1003.75 * 4.5 / 100 / 12 = $3.76
new balance = $1003.75 + $3.76 = $1007.51
After third month: interest earned = $1007.51 * 4.5 / 100 / 12 = $3.78
new balance = $1007.51 + $3.78 = $1011.29
So, after 3 months we will have $1011.29 in our account and we will have earned $11.29.

If you want something where you can actually use only one calculation for any number of months, that's a challenge but possible...if I had VB installed I'd have a go but I don't :-)

I think that (if you didn't want compound interest) it can be achieved using something along the lines of ((100 + ([yearly interest /12]*[months]))/100)*money

That should do it if it wasn't compound...if yearly interest was 12% (for simplicity sake) it would mean that for a 5 month interest calculation on $1000 you would get $1000 x 1.05 which is $1050 (just mental arithmatic, I'm not actually testing this)...doing COMPOUND interest is more of a hassle and the easiest way would be to use a loop.

I *think* there might be a way to multiply a number to get a compound interest modification value (that you could use to multiply the base cash value to get the end result) but without using VB I won't be able to work it out :-)

I don't know why... but what Rob says should work... anyway try this way around:

VB Code:

Private Sub cmdCalculate_Click()
dim i as long  '*** Maybe that was the problem of not being defined...
txtNewBalance.Text = txtAccountBalance.Text
txtProfit.Text = 0
For i = 1 To Val(txtDuration.Text)
    txtNewBalance = Val(txtNewBalance) * (1 + 4.5 /(100*12))
Next
txtNewBalance = Format(txtNewBalance.Text, "currency")
txtProfit = Format(txtNewBalance - txtAccountBalance.Text, "currency")
End Sub

FV = P(1 + r)ⁿ

Where:
FV = Future Value
P = Principle
r = interest rate (decimal form)
n = compounding periods

* sorry posted wroing formula ^^

ahh thank you so much guys very much appreciated. :) :thumb:

RATED!!!!!! :bigyello: