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Mortgage Affordability Calculator

A mortgage affordability calculator estimates the loan and purchase price supported by a monthly housing budget. It applies a front-end housing ratio and a total debt-to-income ratio, then subtracts taxes, insurance, HOA dues, and mortgage insurance before converting the remaining payment to principal.

Updated 2026-07-09Reviewed by US Finance Hub Editorial TeamCalculations run in your browser

Quick answer

The lower of your housing-ratio limit and total-debt limit sets the planning budget. Lenders use additional underwriting rules, so this is an affordability scenario rather than an approval.

Calculator

Enter your numbers

Income before taxes and deductions.
Required non-housing debt payments.
Maximum share of gross income for housing.
Maximum share for housing plus other debt.
Assumed fixed annual rate.
Mortgage term.
Cash applied to the purchase price.
Estimated property tax and homeowners insurance.
Other recurring housing charges.

How to use this calculator

  1. Enter gross annual household income.
  2. Add monthly debt payments and planning ratios.
  3. Enter mortgage rate, term, and down payment.
  4. Estimate taxes, insurance, HOA dues, and mortgage insurance.
  5. Review the home-price scenario and stress-test higher costs.

Explanation

What it is

A mortgage affordability calculator estimates the loan and purchase price supported by a monthly housing budget. It applies a front-end housing ratio and a total debt-to-income ratio, then subtracts taxes, insurance, HOA dues, and mortgage insurance before converting the remaining payment to principal.

How it works

The calculator creates two monthly limits, chooses the lower one, subtracts non-principal housing costs, and converts the remaining principal-and-interest payment into a loan amount using fixed-rate amortization.

When to use it

Use the mortgage affordability calculator when comparing options, setting a realistic target, or checking whether a proposed financial decision fits your broader plan.

Limitations

  • The result is an estimate based on the amounts, rates, timing, and assumptions entered.
  • Actual product terms, taxes, fees, eligibility rules, and market conditions can change the outcome.
  • Use official disclosures or a qualified professional before making a binding financial decision.

Key terms

Front-end ratio
Housing costs divided by gross monthly income.
Back-end ratio
Housing plus recurring debt divided by gross monthly income.
PITI
Principal, interest, property taxes, and homeowners insurance.
Mortgage insurance
Coverage that may be required for certain loans or down-payment levels.

Formula

The calculator creates two monthly limits, chooses the lower one, subtracts non-principal housing costs, and converts the remaining principal-and-interest payment into a loan amount using fixed-rate amortization.

Affordable housing = min(income × front ratio, income × back ratio − other debt); loan = present value of available mortgage payment

Worked example

With $100,000 income, $750 in monthly debt, conservative ratios, a 6.5% mortgage, and $950 of monthly taxes and other costs, the estimated purchase price depends heavily on the down payment and rate.

FAQ

How much house can I afford on $100,000 a year?

It depends on debts, rates, down payment, taxes, insurance, HOA dues, credit, and lender rules. This calculator turns those assumptions into a planning range.

What debt-to-income ratio do mortgage lenders use?

Limits vary by product and borrower. Common planning ratios are not universal approval standards, and automated underwriting may consider compensating factors.

Does affordability include property taxes and insurance?

Yes. Enter monthly estimates because these costs reduce the amount available for mortgage principal and interest.

Why does a higher mortgage rate reduce the price I can afford?

At a fixed monthly budget, a higher rate directs more payment to interest, so it supports a smaller principal balance.

Should I buy at the maximum amount shown?

Not necessarily. Leave room for maintenance, utilities, moving, savings, income changes, and goals that lender ratios do not measure.

Common mistakes

  • Using an advertised rate without checking whether it applies to the full balance or term.
  • Leaving out fees, taxes, timing differences, or irregular cash flows.
  • Treating a planning estimate as a guaranteed quote or final professional calculation.

Tips

  • Run a conservative scenario as well as an optimistic one.
  • Change one assumption at a time so you can see what drives the result.
  • Save or export the calculation and update it when rates, costs, or goals change.

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Sources and editorial review

Educational estimates only; not personalized financial, tax, legal, lending, investment, or insurance advice.