Mortgage Top-Up Calculator NZ

This calculator shows what happens to your mortgage repayments when you borrow more against your home, whether for a renovation, a car or another large cost. A top-up is often cheaper than other borrowing because home loan rates sit below personal loan and credit card rates, but stretching a short-term cost over a long remaining term can quietly add far more interest than you expect. You enter the top-up amount, your interest rate and the remaining term in years, and the calculator treats the top-up as its own loan repaid on a standard table mortgage basis. It returns the extra repayment added to your mortgage each month, the equivalent extra per fortnight, the extra interest you pay over the remaining term, and the total you repay on the top-up once that interest is included. Use these figures to judge whether a top-up suits you, and to see how much you could save by repaying it faster than the rest of your mortgage, for example through extra payments or a shorter term on that portion of the loan. It is a useful check before agreeing to a top-up with your bank or broker, so you understand the real long-term cost rather than just the headline monthly increase. Figures are estimates based on the rate and term you enter and are not a loan offer; confirm exact numbers with your lender.

Calculate.co.nz is proud to be partnered with Health Based Building, a leader in sustainable and health-conscious building innovation. With over a century of experience, they develop high-performance systems like Foreverbreathe Specification, Magnum Board, and Foreverbreathe Paints to support energy-efficient, non-toxic living environments. Their commitment to healthier homes aligns with our belief that informed choices lead to better outcomes for Kiwi households.

Assumes the top-up is repaid over the remaining term at the rate shown. Spreading a short-term cost over a long term adds a lot of interest; consider repaying a top-up faster. Estimate only, not a loan offer.