House Affordability Calculator
Estimate a maximum home purchase price under standard 28%/36% debt-ratio assumptions, from your income, existing debt, down payment, and mortgage rate.
Calculator Inputs
Sets the currency this calculator's numbers are denominated in. This is presentation only — it does NOT convert your numbers between currencies, it only changes how they're formatted.
Gross (pre-tax) annual household income.
Recurring monthly debt payments (auto, cards, student loans), excluding housing.
Cash available for a down payment.
Expected annual mortgage interest rate.
Add 0-11 extra months to the term selected above, for a more precise estimate.
- Maximum Home Price
- $372,242.72
- Conservative Monthly Payment
- $2,100.00
- Maximum Loan Amount
- $332,242.72
- Which Limit Applies
- 28% front-end housing ratio
About these results
CalcSpectrum calculators produce automated estimates using established formulas and the specific values you enter. Because real-world outcomes depend on input accuracy, mathematical assumptions, and rounding conventions, please verify critical figures with an appropriately qualified financial, tax, medical, legal, or other professional, as relevant.
Financial Notice: These figures are informational estimates for personal planning only. They do not constitute financial, investment, tax, or legal advice, nor do they represent a lending offer or credit approval. Provider and financial institution figures, rates, fees, and underwriting requirements may differ.
How It's Calculated
Formula
This calculator estimates how much home you can afford using two standard debt-ratio conventions — neither is a jurisdiction rule or a specific lender's real approval cutoff. The front-end ratio caps the housing payment alone at 28% of gross monthly income. The back-end ratio caps total debt (housing plus existing obligations) at 36% of gross monthly income. Whichever of the two produces the lower maximum monthly payment is the binding constraint. That maximum payment is then converted into a maximum loan amount using the exact algebraic inverse of the standard mortgage-payment formula — the same formula an amortization schedule is built from, solved here for principal instead of payment. Adding your down payment to that loan amount gives the maximum home price.
Worked Examples
$90,000 income, $300/month debt, $40,000 down, 6.5% rate, 30-year term
- Gross monthly income: 90,000 / 12 = $7,500
- Front-end cap: 7,500 × 0.28 = $2,100
- Back-end cap: (7,500 × 0.36) − 300 = 2,700 − 300 = $2,400
- Max allowed payment: min($2,100, $2,400) = $2,100 — the front-end ratio binds
- Max loan principal (6.5%/12 monthly rate, 360 payments): ≈ $332,243
- Max home price: 332,243 + 40,000 ≈ $372,243
Same income and terms, but $2,500/month existing debt
- Front-end cap is unchanged: $2,100
- Back-end cap: 2,700 − 2,500 = $200 — much lower now
- Max allowed payment: min($2,100, $200) = $200 — the back-end ratio now binds
- Max loan principal at $200/month: ≈ $31,642; max home price: 31,642 + 40,000 ≈ $71,642
Frequently Asked Questions
Are the 28% and 36% ratios official lending requirements?
No — they're widely cited financial-literacy conventions, not government regulations or any specific lender's actual underwriting standard. Real mortgage qualification varies by lender, loan program, credit profile, and other factors this calculator doesn't model.
Why does more existing debt lower my maximum home price?
The back-end ratio caps TOTAL monthly debt (housing plus everything else) at 36% of income. The more of that 36% budget your existing debt already uses, the less room is left for a housing payment — which directly shrinks the loan amount, and therefore the home price, you can support.
Does the maximum home price include property tax, insurance, or HOA fees?
No — this calculator solves for loan principal from principal-and-interest payments only. Property tax, homeowners insurance, mortgage insurance, and HOA dues would reduce the payment available for principal and interest, and are not modeled here.
What if my maximum allowed payment comes out to $0?
That happens when existing debt payments alone already meet or exceed the 36% back-end budget — the calculator reports $0 (not a negative number) and a maximum home price equal to just your down payment, signaling no additional financed amount fits the standard guideline.