What this calculator does
It builds the full monthly cost of a specific house, compares it against what your income can carry, and checks whether you would still have cash left afterwards. Three things go into it that most affordability tools leave out.
PMI, because below 0.2% equity a lender adds it and it changes the monthly figure materially. It is modelled with an end date rather than forever, since it must come off at 0.78% loan-to-value on most conventional loans.
Maintenance, at 1% of value a year. No lender counts it because no lender is paying it. It is usually larger than the insurance and HOA lines that every competitor itemises carefully.
A reserve test. Whether 3 months of housing costs remain in cash once the deposit and closing costs are paid. A purchase can clear every lender ratio and still leave you one boiler away from a credit card balance.
When the answer is no
The calculator does not stop at a verdict. It solves three levers independently, each holding the others still: the income that would make this house work, the deposit that would, and the interest rate that would. That turns an unaffordable house into a decision with numbers attached, which is usually either a target to save towards or a reason to look at a different price bracket.
What each input means
- House price. The specific listing you are weighing up.
- Household income. Gross, before tax, from everybody going on the loan.
- Deposit. Cash going in upfront. Below 0.2% of the price, PMI is added automatically.
- Existing monthly debt. Cards, car loans, student loans. Not everyday spending.
- Rate and term. Used to turn the loan into a monthly payment.
- Savings after the deposit. What feeds the reserve test.
Frequently asked questions
How is this different from a mortgage affordability calculator?
It runs the question in the other direction. A mortgage calculator starts from your income and tells you the most you could reach. This one starts from a specific house and tells you whether you can afford that one, which is the question people actually have when they are looking at a listing.
Why does it include maintenance when no lender does?
Because a lender is protecting its loan, not your budget. Upkeep at the common 1% of value a year is larger than most of the escrow lines every competitor itemises carefully, and it is the reason houses that pass a lender's test still feel unaffordable to live in.
What is PMI and when does it stop?
Private mortgage insurance, which a lender adds when you put down less than 0.2%. It is the whole difference between the 20%-down case and every other one. On most conventional loans it must be removed automatically at 0.78% loan-to-value, so it is a temporary cost with a knowable end date rather than a permanent one.
What is the reserve test?
Whether you would have 3 months of housing costs left in cash after paying the deposit and closing costs. It is not something a lender requires at this level, and it is the difference between owning a house and being owned by one. Plenty of purchases pass every lender check and fail this.
What does the calculator do when the answer is no?
It prices the gap rather than telling you to save more. Three levers are computed independently, each holding the others still: how much more income you would need, how much larger a deposit would do it, and what interest rate would make it work. "Save more and pay down debt" is not an answer; a number is.
Is this a pre-approval?
No. It is a planning estimate from the figures you enter. A lender will also weigh credit history, employment, assets and its own underwriting rules, any of which can move the answer either way.
Read more
The full write-up, including what a $700,000 house costs every month at 20%, 10% and 5% down, is in how much salary you need to afford a $700k house. To run the question the other way and find the most your income can reach, use the salary and mortgage calculator. If a second child is part of the same decision, the cost of another child.
A planning estimate, not a mortgage pre-approval or an offer of credit. Maintenance and escrow figures are estimates rather than bills.