The repayment formula
A Hong Kong mortgage is an amortising loan: you pay the same amount every month, split between interest on the balance still outstanding and repayment of the principal. Early on almost all of it is interest; by the end almost all of it is principal. The payment itself falls out of the standard annuity formula, and the loan amount, the monthly rate and the number of months are the only three things that determine it — which is why this calculator asks for nothing else. The arithmetic runs as compiled code shared with our other property tools, so the figure here and the figure in the buy-vs-rent comparison cannot disagree.
What you can borrow: the 70% cap
The HKMA caps a residential mortgage at 70% of the property's value, so the baseline deposit is the rest. Since 16 October 2024 that cap has been flat — the same for every residential property, whatever the price, and whether or not you will live in it. Before that date it was tiered by value and by self-occupation, so a calculator still applying the old tiers under-lends on exactly the flats buyers ask about. The Mortgage Insurance Programme can lift the borrowing share above the cap for eligible buyers, at a premium.
What your income can carry: the 50% ratio
Separately, your total monthly debt repayments may not exceed 50% of your monthly income. For a first purchase in Hong Kong that limit usually binds before the deposit does, and existing borrowing counts toward it — which is why a bank's number is often lower than a calculator's. Our affordability calculator inverts this page: instead of pricing a loan you name, it works out the largest loan your income and deposit support, and says which of the two limits produced the answer.
The stress test, and its actual status
Hong Kong mortgage calculators conventionally show a second figure at the quoted rate plus 200 basis points. That was a real HKMA requirement, and it was suspended on 28 February 2024; it is not a condition of approval today. We still show the stressed repayment, but as your own prudence rather than a rule — if a two-point rise would break the budget, that is worth knowing whether or not a regulator asks.
H-plan or P-plan: which rate to enter
An H-plan prices off HIBOR, the interbank rate, plus a spread, and carries a cap tied to the bank's prime-based rate. A P-plan prices off prime less a discount. Most borrowers are on an H-plan and pay the cap whenever HIBOR runs high, so the rate you actually pay moves. Enter the effective annual rate you are quoted — then run the page a second time at the cap, and read the two answers as the range you are signing up for.
What the monthly repayment does not include
Principal and interest, and nothing else. Rates and government rent are billed quarterly by the Rating and Valuation Department, management fees monthly by the building's manager, and fire insurance annually — none of them appear in the figure above, and together they are not a rounding error on the true monthly cost. Our rates and government rent calculator works the quarterly bill out from the rateable value.
Why the total interest looks so large
Stretching the term lowers the monthly payment and raises the total interest, because you are borrowing the same money for longer. Thirty years is the usual maximum on a Hong Kong residential mortgage, and the term you can actually get also depends on the age of the property and on yours. Run the same loan over 20, 25 and 30 years above: the monthly figure moves a little and the total interest moves a lot.
