PropLeh

How Our Numbers Work

Every calculator on PropLeh states the rule it's applying and where that rule comes from, so you can check the working rather than just trusting the result. This page walks through the formulas behind each tool and links to the MAS, HDB, CPF and IRAS pages they're built on.

⚠ These are the rules as we've implemented them, not a substitute for them. Regulations, rates and thresholds change — always check the linked source for the current figure, and confirm with your bank, HDB, CPF Board or your lawyer before relying on any number here.

Max Loan Assessor Option Analysis Sale Proceeds — HDB Sale Proceeds — Private

Buying

Max Loan Assessor

Answers: how much can I borrow, given my income and existing debt? This follows MAS's Total Debt Servicing Ratio (TDSR) and Mortgage Servicing Ratio (MSR) framework, the same framework every bank in Singapore uses to assess a home loan.

Core formula

Max Loan = Affordability Budget × Present-Value Annuity Factor (MAS stress-test rate, loan tenure)

Private property → Budget = TDSR limit = 55% of Assessable Income − Monthly Debt
EC / HDB Resale  → Budget = lower of (MSR limit = 30% of Assessable Income) and (TDSR limit)

Assessable IncomeFixed monthly income counted in full; other annual income (bonus, commission, rental, dividends, director's fees, etc.) is annualised and divided by 12, in line with MAS TDSR guidelines on assessable income.
Stress-test rateLoan eligibility is computed at a fixed MAS medium-term interest rate floor (currently 4% for a residential mortgage), not your bank's quoted rate — this is what actually caps your loan, so a lower quoted rate mainly lowers your monthly instalment, not your maximum loan.
Loan-to-Value (LTV)Capped by MAS at 75%/55% for a 1st housing loan, 45%/25% for a 2nd, 35%/15% for a 3rd — the lower figure in each pair applies once tenure exceeds 30 years (private/EC) or the borrower is over 65 at loan-end.
Tenure caps30/35 years for private & EC, 25/30 years for HDB resale, further capped so income-weighted average age + tenure ≤ 65 (higher LTV band) or ≤ 75 (lower LTV band).
CPF OA contributionShown for reference only, at each applicant's age-tiered CPF Ordinary Account allocation rate against the CPF Ordinary Wage ceiling.

Sources

Buying

Option Analysis

Answers: which property option — New Launch or Resale, invest or own-stay — actually returns more? Buying costs, financing and the payment timeline are modelled explicitly, then compared on both an unlevered and a levered (IRR) basis.

Returns

Unlevered Return  = IRR of (buying costs + full price paid in cash, on the same payment timeline) vs (net sale proceeds)
                    → isolates pure price growth, no loan involved

Levered Return    = IRR of your actual cash/CPF outlay, loan interest as serviced, and outstanding
  (IRR)              loan payoff at sale vs net sale proceeds
                    → the return on your own money, given the effect of financing

Buyer's Stamp DutyIRAS's tiered bands on the purchase price: 1% on the first $180k, 2% on the next $180k, 3% on the next $640k, 4% on the next $500k, 5% on the next $1.5m, 6% on the remainder.
Add'l Buyer's Stamp DutyApplied on top of BSD, based on the Buyer Profile you set — residency status (SC/PR/Foreigner) × property count — at IRAS's current ABSD rate table.
Seller's Stamp DutyApplied automatically if the modelled holding period is under 4 years, on IRAS's current tiered schedule (16% within 1 year, down to 4% in year 3–4, nil after).
New Launch payment scheduleThe standard progressive payment schedule: 5% booking fee, 15% on S&P Agreement, 5% at Foundation (cash), then loan-funded stage draws through to TOP (25%), and the final 15% at CSC, 12 months after TOP.
Resale paymentModelled as fully disbursed at completion, roughly 8–10 weeks after the Option is exercised.
Loan amortisationA standard monthly, reducing-balance mortgage at your chosen tenure and rate, drawn down against each stage payment.
Rental incomeOnly counted from the month a unit is tenantable (immediately for resale, after TOP for a new launch), net of your marginal IRAS income-tax bracket on rental income.

Sources

Selling

Sale Proceeds — HDB Resale

Answers: what will I actually walk away with after selling my HDB flat? Follows HDB's resale process from Intent to Sell through to Completion, and CPF Board's refund computation.

Core formula

Gross Sales Proceeds  = Selling Price − Outstanding Loan − Total CPF Used (principal + accrued interest)
Gross Cash Proceeds   = Gross Sales Proceeds   (CPF is refunded separately to your CPF account, not paid out as cash)
Net Cash Proceeds     = Gross Cash Proceeds − Total Expenses

CPF refundEvery dollar of CPF principal used to buy the flat, plus the accrued interest it would have earned had it stayed in your CPF account, is refunded to your CPF Ordinary Account (or Retirement Account, from age 55) before any cash reaches you.
Resale levyOnly payable if you previously received a housing subsidy and this is your second subsidised flat — deducted here if you complete this sale before buying your next flat.
Outstanding HIPAny unpaid Home Improvement Programme instalments owed to HDB are recovered from your sale proceeds.
Seller's Stamp DutyRarely applies to HDB resale, since the 5-year Minimum Occupation Period already exceeds SSD's holding-period window — modelled here for the rare exception (e.g. an MOP-exempt inheritance or divorce transfer).
TimelineMirrors HDB's actual process — Intent to Sell (1 wk) → OTP issued, Option Fee received (21 days) → OTP exercised, Exercise Fee received (7 days) → Resale Application (2–4 wks) → Seller's Endorsement, most expenses settled here (8 wks) → Sales Completion, balance proceeds received.

Sources

Selling

Sale Proceeds — Private Residential

Answers: what will I walk away with after selling a private property? Follows the standard Option to Purchase → Exercise → Completion path used for private resale transactions, and CPF Board's refund computation.

Core formula

Gross Sales Proceeds  = Selling Price − Outstanding Loan
Gross Cash Proceeds   = Gross Sales Proceeds − Total CPF Used (principal + accrued interest)
Net Cash Proceeds     = Gross Cash Proceeds − Total Expenses (SSD + bank's penalty + legal fee + other costs)

CPF refundSame principle as HDB — CPF principal used plus the accrued interest it would have earned is refunded to your CPF account, deducted from proceeds before cash reaches you.
Seller's Stamp DutyApplies if you sell within the SSD holding period from your purchase date, at IRAS's current tiered schedule for residential property (16%/12%/8%/4%/nil, by year of sale). Older purchases may fall under an earlier IRAS schedule — worth confirming directly.
Bank's penaltyEarly redemption / prepayment penalty, applicable only if you're still within your loan's lock-in period.
TimelineOption to Purchase issued, typically 1% of price received (2 wks) → OTP exercised, typically a further 4% received and expenses settled (12 wks) → Sales Completion, CPF refunded and balance cash proceeds received.

Sources