FinTools4U

Home Affordability Calculator

Estimate a home price from income, other debts, down payment, and the housing share of income you are willing to use.

Key concepts

Front-end ratio

Housing payment divided by gross monthly income. A common teaching default in the United States is 28%. You can move the slider.

Back-end ratio

Housing payment plus other monthly debts, divided by gross income. A common teaching default is 36%. The tighter of the two caps wins.

What this tool does

Payment capacity, then a price

The page caps the housing payment at the lower of your front-end limit and what is left of the back-end limit after other debts. Tax and insurance you type are subtracted next. What remains is principal and interest, which the fixed-rate formula turns into a loan. The price adds your down payment. The PMMS 30-year chip fills Freddie Mac’s survey average, shows the survey date, and leaves the rate field editable.

Not a lender decision

Banks use credit, reserves, and their own ratios. This model does not. Scenario B compares another term or another rate — 30 years beside 15, for example. The chart moves the rate and redraws the price.

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Affordability formula

Housing cap = min(income × front, income × back − other debts)
P&I = housing cap − tax − insurance
Loan from the fixed-rate payment formula
Price = loan + down payment

The loan inversion is the same principal-and-interest formula as the mortgage payment calculator, solved for the amount instead of the payment. Tax and insurance are flat monthly amounts. They do not grow, and they are not looked up from an address. A zero result means the ratios leave no room for a housing payment.

Worked example

Gross income of 5,000, no other debts, 20,000 down, a 0% rate, 30 years, a 28% front-end, and a 36% back-end. The housing cap is 1,400. With no tax or insurance, the loan is 1,400 × 360 = 504,000 and the price is 524,000. Add other debts and the back-end limit can become the one that binds.

Affordability versus the payment calculator

Question

This affordability tool
How much house fits the income?
Payment calculator
What is the payment on a known loan?

Loan amount

This affordability tool
Solved from the payment cap
Payment calculator
You type it

Common mistakes

  • Using net pay when the ratios are defined on gross income.
  • Ignoring the debts you already pay. The back-end ratio exists for that.
  • Treating the price as an approval. Credit, cash reserves, and lender rules sit outside this page.

Methodology on this page

Housing payment is the minimum of the front-end and back-end caps. Principal and interest is that payment minus the tax and insurance you enter. The loan is the fixed-rate formula inverted, with the nominal annual rate divided by 12. Price adds the down payment. Educational only — not a pre-approval and not financial advice.

Read the full FinTools4U methodology →

Frequently asked questions

Why do 28% and 36% show up?

They are a common teaching pair for housing and total debt in the United States. The sliders move. Portuguese and Spanish pages start from local teaching defaults, and the formula stays the same.

Does the down payment reduce the loan?

Yes. The loan is what the payment can support. The price is that loan plus the cash you put down.

Where do taxes and insurance go?

They reduce the principal and interest the payment can cover. They are not estimated from an address, and they do not change with the home price inside this model.

Is this financial advice?

No. It is an educational ceiling. A lender’s approval is a different document. PMMS 30-year fills the mortgage rate from the Freddie Mac survey, shows the survey date, and you can still edit the field. The link stores the number you apply. Indicative rate, not a recommendation.

Sources & further reading

  • CFPB — Owning a Home — Borrower-facing context for mortgage payments. Lender ratios can differ from the sliders.

Related guide

How much home you can afford

Front-end and back-end ratios, the loan those ratios support, and how to read the FinTools4U home affordability calculator.

How rent versus buy is calculated

Net cost of owning and renting over a horizon you choose, what the optional rates change, and when the FinTools4U comparison is not enough.

Related calculators

Mortgage Payment

Price the principal-and-interest payment once you have a loan amount.

Amortization Schedule

See how that payment splits into principal and interest each month.

Refinance Break-even

Later, compare a new rate with the balance you still owe.

Savings Goal

Build the down payment before you stretch the price.

Emergency Fund

Keep a reserve beside the housing payment.

Inflation and Real Return

A long loan is a nominal payment. Prices around it still move.

Rent vs Buy

Once a price is in range, compare that stay with the rent you would pay instead.