Calculate how many years earlier you can clear your mortgage and how much interest you save by paying extra each month, showing the long-term benefit of larger payments.
Input Data
Results
At a glance:Extra payments reduce the outstanding principal faster, shortening the term and cutting the total interest under a reducing-balance schedule.
Formula
monthlyPayment = P × r·(1+r)^n / ((1+r)^n − 1) (r = annualRate/12, n = years×12)
Re-run the amortisation with monthlyPayment + extraMonthly to find payoffMonthsWithExtra and totalInterestWithExtra.
yearsSaved = years − payoffMonthsWithExtra/12
interestSaved = originalTotalInterest − totalInterestWithExtra
How to Use
- Enter the loan principal, annual rate, and term.
- Enter the extra monthly principal.
- Review the payoff months, years saved, and interest saved.
FAQ
Does paying a little extra really make a big difference?
Yes. Because the extra payment goes entirely to principal, it reduces the interest charged in every later period, and the effect compounds over time. Even a few thousand extra a month can clear a 30-year mortgage several years early and save hundreds of thousands in interest; the earlier you start, the greater the effect.
What is the difference between extra payments and shortening the term?
Both save interest. Flexible extra payments let you raise or pause them with your cash flow, free of the contract term; shortening the term raises the fixed monthly payment and saves interest more definitively but with less flexibility. This tool simulates the flexible extra-payment approach.
What should I check before adding extra payments?
Hong Kong mortgages usually have a penalty period; large early repayments within the first 2–3 years may incur a penalty or fee, so check the contract first. Also keep a sufficient emergency reserve and weigh the opportunity cost of the cash versus other investments before deciding how much extra to pay.
What must I confirm before adding extra payments, and could it backfire?
Adding extra payments saves a lot of interest, but confirm three things first or you may face a penalty or sacrifice liquidity. First, the penalty period and early-repayment terms: Hong Kong mortgages usually impose a penalty in the first 2–3 years, during which large early repayment or refinancing may trigger a penalty and a clawback of the cash rebate; some plans cap the annual penalty-free prepayment portion. Check the contract before adding (large) extra payments, and use the Mortgage Penalty Calculator to estimate the cost. Second, your emergency reserve and liquidity: once money goes into the mortgage it is hard to take back out (unless you refinance and redo the stress test), so keep enough emergency fund (typically 3–6 months of expenses) and do not pour all spare cash into extra payments. Third, the opportunity cost: if your mortgage rate is low and you can earn a higher, reliable return elsewhere, or you have more urgent financial goals, rushing to add extra may not be necessary. Only when there is no penalty, your emergency fund is adequate and there is no better use for the cash is adding extra a sound interest-saving choice. With the high 6.5% rate in this example the saving is especially pronounced, but the actual benefit depends on your own rate.
What is the difference between extra payments and directly 'shortening the term', and which should I choose?
Both save interest and pay off early by the same principle (speeding up principal repayment), differing mainly in flexibility and commitment, so pick by your personality and cash flow. Flexible extra payments (this tool's model): you decide how much extra to pay each month beyond the standard payment and can raise, lower or pause it with your cash flow, free of the contract term. The upside is flexibility and low pressure, suiting those with uneven income or who prefer to go at their own pace; the risk is that without discipline you may slacken and dull the saving. Directly shortening the term (applying to the bank to shorten the repayment period): e.g. from 30 to 20 years, the monthly payment rises and stays high — the saving is most definite and acts like forced saving; but the higher payment becomes a contractual obligation with less cash-flow flexibility, and shortening usually requires redoing the income assessment and stress test. Practical advice: if you are disciplined and sure you can afford the higher payment long term, shortening the term is most direct; if you want flexibility and to add extra with the cash flow, use extra payments (this tool). The two can also be combined.
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.