Ask a lender what you can afford and you get a payment. Ask your future bank account and you get a stack: the mortgage, yes — plus property tax, home insurance, HOA or community fees, and the maintenance a building extracts whether you budgeted for it or not. On a typical purchase the mortgage is only about two-thirds of the true monthly cost of owning, and buyers who budget for the payment alone discover the other third the hard way. This calculator works from the property, not from income ratios: enter a price and it stacks every monthly cost, shows the cash needed up front, and compares 10%, 20% and 30% down payments side by side. Or flip it around — enter the total monthly amount you can genuinely carry, and it solves for the highest price that keeps the whole stack inside it.
A 300,000 home, honestly costed
With 20% down, the loan is 240,000 and at 6% over 30 years the mortgage is 1,438.92 a month — the number every affordability discussion stops at. Keep going: property tax at 1.1% of the price is 275.00 a month, insurance at 1,800 a year is 150.00, HOA is 60.00, and a maintenance allowance of 1% of the price a year is 250.00. The true monthly cost is 2,173.92 — the mortgage is 66% of it. Cash up front: 60,000 down plus 2% closing costs, 66,000 in total. The scenario table shows the down-payment trade in full: 10% down drops the cash needed to 36,000 but raises the true monthly cost to 2,353.79; 30% down needs 96,000 up front and brings the month down to 1,994.06. And the budget mode confirms the stack from the other side: a total budget of 2,173.92 a month, with these same rates and percentages, carries a price of almost exactly 300,000 — because that is the price the budget was built from.
One more line when the down payment is small
Below 20% down, many lenders add mortgage insurance to the stack — a monthly premium that protects the lender, not you, and typically falls away once the balance drops under 80% of the value. It belongs in this calculation while it lasts: add it to the HOA line as a temporary extra, run the numbers, then run them again without it to see the month your cost drops. The scenario table makes the trade visible — a smaller down payment preserves cash today at the price of both a bigger loan and, often, this extra premium riding on top of it.
Why the percentages matter more than the payment
Tax, insurance and maintenance are entered as percentages of the price (insurance as a yearly figure) precisely because they grow with the home you buy. A buyer stretching from 300,000 to 340,000 does not just add mortgage; at these rates they add about 290 a month of true cost, of which the mortgage is only about 191. This is also why two homes at the same price can cost very different amounts to own: a low-tax, no-HOA house and a high-fee condo in a high-tax district may share a listing price and differ by hundreds a month in carrying cost. The calculator cannot know your local tax rate or your building’s fees — ask the seller, the agent or the municipality, and enter real figures rather than the defaults.
How this differs from a lender’s affordability answer
A lender’s borrowing-cap calculation starts from your income and debt ratios and returns the largest payment it will approve — approval, not comfort. This tool starts from the property and returns what owning it will actually extract each month; whether that fits your income is a judgement only you can make, ideally with a margin for the boiler, the roof and the year the car also dies. Use the two together: the borrowing cap tells you the ceiling the bank allows, this stack tells you the floor your budget must clear, and the right purchase price is the one that satisfies both with room to spare.
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Versión en español: Calculadora del Coste Total de Comprar una Vivienda: Cuota, IBI, Seguros, Comunidad y Mantenimiento · Mortgage Affordability (Borrowing Cap) Calculator.
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