If you are trading in your existing vehicle on the new vehicle it depends on how you plan to use the trade-in money as to how you allow for it when entering the loan amount. If you choose to deduct the trade-in price directly from the purchase price of the car and get a Chattel Mortgage for the balance of what is owing on the new car, you will need to estimate what you think you may get as a trade-in and deduct that from the loan amount you enter. You can refer to valuation guides or request a trade-in offer before using the calculator or simply work on your own guesstimate. Another way of approaching a trade-in is to have the dealer give you the money in cash and borrow 100% of the purchase price of the car. If you choose that option, simply enter 100% of the purchase price of the car into the calculator.