# interest & princiapl portion of a payment

#### missl

##### New member
Hi people, I was just wondering if I want to just find a certain interest and principal portion of a payment for example like on a 50 payment. How would I do that instead of going through the whole chart? That would take a long time to do. Is there a formula that can be used?

#### Denis

##### Senior Member
missl said:
Hi people, I was just wondering if I want to just find a certain interest and principal portion of a payment for example like on a 50 payment. How would I do that instead of going through the whole chart? That would take a long time to do. Is there a formula that can be used?
You were told how before, in your topic "calculating interest and principal components":
> Formula for interest during a given period:
> Total payments - (opening balance - closing balance).

On a 50th payment, you would use the balances owing after 49 and 50 payments.
payment amount - (49th balance - 50th balance).

Example: payment=100, 1022 is amount owing at 49th payment, 965 is amount owing at 50th payment:
100 - (1022 - 965) = 100 - 57 = 43