About this calculator
The National Credit Act obliges every bank to assess affordability before granting a bond — but it deliberately sets no ratio. What has hardened into market practice is a two-part test. First, the total bond repayment should sit around 30% of gross monthly income. Second, and more powerful in practice, the surplus test: after tax-typical living expenses and every existing debt instalment, enough surplus income must remain to service the new bond with a margin. That is why two applicants on identical salaries get different approvals — the one with a R9,000 car instalment fails a test the salary alone passes.
This calculator labels its inputs for what they are: practice, not statute. The 30% figure is the widely used guideline banks start from; the surplus line assumes living expenses of roughly 25% of gross income where you have not itemised them (banks substitute their own expense tables, or your declared expenses if higher); and the stressed row re-prices your ceiling at two points above your rate, because approval committees think in prime-plus-buffer terms even when they quote you prime-minus. Treat the binding (smallest) figure as the planning number, and the comfortable 25% row as the ceiling that survives a rate-hiking cycle.
How to use it
- Enter gross monthly income — banks work from gross, not take-home, for the ratio tests.
- Add every other monthly debt payment honestly: car, cards, personal loans, store accounts. The bank will see all of them on your credit bureau record anyway.
- Compare the table rows: the smallest loan is the one a credit committee recognises; the note tells you which test bound.
- Use the affordability answer with the costs calculator — qualifying for the bond is not the same as holding the upfront cash.
The formula
On a R65,000 gross income with R6,000 of other debts: the 30% rule allows a R19,500 repayment; the surplus line allows R42,750, so the 30% rule binds. R19,500 a month at 11% over 20 years is a bond of R1,889,190. Re-run at a stressed 13% and the same payment supports only R1,664,425 — roughly R225,000 of headroom the bank is keeping against a hiking cycle, and the reason offers can look conservative next to headline calculators.
Worked example
A couple on a joint R95,000 gross income with one car instalment of R7,500: the 30% rule budgets R28,500 a month, the surplus line R63,750 — the rule binds, and at 11% over 20 years they qualify around R2.76 million before the bank’s own margin. Drop the car (or settle it) and nothing changes on the ratio row — but their surplus, their credit score treatment and their chances of a prime-minus rate all improve, which is why settling small debts before applying is the oldest advice in the South African market.
Sources: National Credit Act 34 of 2005 affordability-assessment obligations and published South African bank practice (repayment-to-income guidelines, surplus-income tests and stress buffers), described as practice rather than law, current October 2026. Last updated: October 2026.
Frequently asked questions
Is the 30% rule a law in South Africa?
No. The National Credit Act requires an affordability assessment and prohibits reckless lending, but prescribes no percentage. The ~30% of gross income repayment guideline is bank practice that has become the market convention, applied alongside the surplus-income test. A bank may go above it for a high-income applicant with a large surplus and a clean record — or below it where expenses are heavy.
Why do banks ask for three months of bank statements?
To verify the surplus test against reality rather than your declarations: salary credits, actual living expenses, debit orders and any debt payments you did not list. Banks compare your stated expenses with their own minimum-expense tables (linked to income) and generally use the higher figure. Undisclosed debts surface in the statements or the credit bureau check and can collapse an approval at the final stage.
Do 100% bonds change the affordability answer?
The bond amount you qualify for is set by the same tests; a 100% bond just spends all of it on the price, leaving nothing covered for costs and usually attracting a higher rate margin. First-time buyers are the main recipients. If the stressed row of this calculator is below the price you are chasing, a 100% bond does not rescue the purchase — it concentrates the risk the stress test is warning about.
How do banks treat commission, overtime or rental income?
Variable income is typically averaged over 6–24 months and often discounted (only a portion counted, or the lower of the periods used). Rental income on an existing property is usually counted at a discount and net of levies and rates. Self-employed applicants are assessed on financial statements and tax returns, and most banks want two years of trading history.
Will pre-approval from a bond originator change the number?
Originators (BetterBond, ooba and the like) run your application past several banks at no cost to you and return real offers — which can differ by a full percentage point of rate for the same applicant. A pre-approval is the assessed, bank-specific version of this calculator’s estimate and the document estate agents take seriously. Get one before you sign an offer to purchase; it costs nothing and binds no one.
What formula does this south africa home loan affordability calculator use?
Payment budget = min(30% × gross income, 75% × gross income − other debts); bond = annuity value of that payment at your rate (and at rate + 2% stressed) On a R65,000 gross income with R6,000 of other debts: the 30% rule allows a R19,500 repayment; the surplus line allows R42,750, so the 30% rule binds. R19,500 a month at 11% over 20 years is a bond of R1,889,190. Re-run at a stressed 13% and the same payment supports only R1,664,425 — roughly R225,000 of headroom the bank is keeping against a hiking cycle, and the reason offers can look conservative next to headline calculators. The worked example on this page applies the formula step by step with real numbers, so you can verify the result by hand.