Monthly loan payments vary based on many factors, including principal, interest rate, length of loan and additional fees or payments added to a loan. The formula can be found on: 1728.com and guardian money (it may be english but it uses the same formula) your repayments can be calculated. The formula is called the amortization calculation, but is a complicated formula but i will explain briefly.

Firstly you need to check you have all the information needed: Annual interest rate, amount and months repaid over.

Your annual interest rate (8%) is turned into a "rate" which is: Annual percentage rate divided by 1200.

- Your rate is 1/150.

- The number of months you will repay over is calculate: Years multiplied by 12.

- The principal is already given, the amount you want to borrow.

- This is then substituted into a large formula:

- rate + {rate / [(1+rate)^months]-1} x principal

Your principal is the amount you borrow ($40,000). When all this is substituted in carefully it returns $382.26. A derivation of the formula can be found upon wikipedia under "Amortization calculator".

For more information about the amount your paying off (if you dare to see it) go to the guardian money website: Money.guardian.co.uk/calculator/form/o,,603119,00.html. And you can see this. This calculator also returns that you will be $28806.95 in interest over the fifteen years.

If you have Microsoft office: Excel the repayments can also be calculated with the function "PMT." It takes the form: "PMT(Interest rate, Number of periods, Principal, Future value (normally 0), Payments due (0)).

Firstly you need to check you have all the information needed: Annual interest rate, amount and months repaid over.

Your annual interest rate (8%) is turned into a "rate" which is: Annual percentage rate divided by 1200.

- Your rate is 1/150.

- The number of months you will repay over is calculate: Years multiplied by 12.

- The principal is already given, the amount you want to borrow.

- This is then substituted into a large formula:

- rate + {rate / [(1+rate)^months]-1} x principal

Your principal is the amount you borrow ($40,000). When all this is substituted in carefully it returns $382.26. A derivation of the formula can be found upon wikipedia under "Amortization calculator".

For more information about the amount your paying off (if you dare to see it) go to the guardian money website: Money.guardian.co.uk/calculator/form/o,,603119,00.html. And you can see this. This calculator also returns that you will be $28806.95 in interest over the fifteen years.

If you have Microsoft office: Excel the repayments can also be calculated with the function "PMT." It takes the form: "PMT(Interest rate, Number of periods, Principal, Future value (normally 0), Payments due (0)).