Compare two mortgage plans side by side for monthly payment and total interest, showing at a glance which is cheaper and the difference between them.
Input Data
Results
At a glance:Plan comparison computes each mortgage's monthly payment and total interest and reports the gap between the two plans.
Formula
payment = P × r·(1+r)^n / ((1+r)^n − 1) (r = rate/12, n = years×12)
interest = payment × n − P
monthlyDifference = paymentA − paymentB
interestDifference = interestA − interestB
$$\_i = \\text{PMT}_i \\times n_i - P_i$$$$\\Delta_{\\text{Monthly payment}} = \\text{PMT}_A - \\text{PMT}_B, \\quad \\Delta_{\\text{Interest}} = \\text{Interest}_A - \\text{Interest}_B$$How to Use
- Enter principal, rate, and term for Plan A.
- Enter principal, rate, and term for Plan B.
- Review each plan's payment and interest and the differences.
FAQ
Should I look at the monthly payment or the total interest?
Both. The monthly payment reflects your immediate cash-flow pressure, while the total interest reflects the long-run cost. A shorter-term plan usually has a higher monthly payment but lower total interest, so weigh it against your own affordability and interest-saving goal.
What else should I consider beyond the rate and term?
Beyond the rate and term, compare the bank's cash rebate, penalty period, mortgage-insurance premium, legal fees and valuation fees — these affect the plan's true total cost and may not be captured by the payment and interest alone.
Why does a longer term cost so much more even at the same rate?
Because the longer you borrow, the more periods interest accrues on. Even at the same rate, a 30-year plan's total interest is far higher than a 20-year plan's — it just has a lighter monthly payment. This calculator quantifies that trade-off directly.
Which number should I check first when comparing plans?
No single figure decides it all; the right approach is 'first check whether the monthly payment is affordable, then see which has lower total interest'. Step one: the monthly payment decides your immediate cash-flow burden and directly affects the bank's approval — the debt-servicing ratio (DSR) usually has a cap and you must pass the rate-rise stress test. If a plan's payment is too high to afford or fails the stress test, a low total interest is meaningless. Step two: among the plans you can afford, compare total interest — the shorter-term, lower-rate one costs less overall. Step three: weigh the two together — some prefer a higher payment for interest savings and an earlier payoff (shorter term), others value cash-flow flexibility and accept more interest via a longer term. Also fold in the cash rebate, penalty period, mortgage insurance, legal and valuation fees, since they change the real cost. This calculator lists payment, interest and both differences side by side precisely so you can see the trade-off at a glance.
Why does the same rate with a different term make total interest diverge so much?
Because interest accrues on the remaining principal month by month; the longer the term, the longer you hold the principal and the more periods it compounds, so total interest rises sharply. Take principal 3,000,000 at 3%: over 20 years, total interest is about HK$993,000; over 30 years, about HK$1,553,000 — an extra HK$560,000, with the rates identical; the gap comes purely from 'borrowing 10 more years'. The longer term's benefit is a lower monthly payment (principal spread thinner, easier cash flow), which is why many choose 30 years; the cost is much higher total interest. So the term choice is essentially a trade-off between 'payment ease' and 'total interest cost', with no absolute right answer — it depends on your income stability, cash-flow needs and willingness to pay off early. This calculator lets you test different terms side by side and quantify the gap directly. Warning: shortening the term pushes up the monthly payment and the stress-test threshold, so confirm affordability first.
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.