Loan Top-Up True Cost Calculator

This calculator shows the true cost of topping up a loan in New Zealand, turning the amount you draw into the extra monthly repayment it adds and the total interest it will cost over the remaining term. A top-up, whether on a personal loan or bolted onto a mortgage, is an easy way to fund a car, a renovation or a holiday, and lenders make it simple precisely because it is profitable for them. The catch is the term: borrowing a few thousand dollars feels small, but stretched over the remaining years of the loan, and especially over a long mortgage, the interest can quietly add up to far more than the purchase itself. You enter the top-up amount, the interest rate and the remaining term in years, and the calculator amortises the new borrowing to find the extra you will pay each month, the total interest, and the total you will repay. The lesson is usually about term rather than rate: even at a low mortgage rate, spreading a short-life purchase over twenty or thirty years multiplies its cost, so a shorter dedicated loan often works out cheaper overall. Use it to weigh the convenience of a top-up against paying cash, saving first, or choosing a shorter repayment term.

Assumes the top-up is repaid over the remaining term at the rate shown. A shorter term cuts the interest sharply. Estimate only, not financial advice.