Mortgage Affordability Calculator
Find out how much house you can afford based on your income, debts, and down payment.
Content updated August 10, 2026
Principal and interest only, under the conventional 28/36 budgeting guideline. Property tax, insurance, HOA dues and mortgage insurance are excluded, so treat this as an upper bound. Lenders commonly approve higher ratios, so this is a planning figure rather than a pre-qualification.
Before you fall in love with a house, it helps to know your ceiling. This affordability calculator estimates the maximum home price and mortgage you can comfortably carry, based on your income, existing debts, and the down payment you've saved.
It applies the conventional 28/36 budgeting guideline, which is deliberately more conservative than the maximum a lender would approve. The result is a planning figure, not a pre-qualification.
The Mortgage Affordability formula
Max payment = min(0.28 × income, 0.36 × income − other debts); Max loan = M × ((1 + r)ⁿ − 1) ÷ (r × (1 + r)ⁿ)income = gross monthly income · other debts = your existing monthly debt payments · M = the affordable monthly payment · r = monthly interest rate (annual rate ÷ 12) · n = number of payments (years × 12). Add your down payment to the max loan for the maximum home price.
Worked example
On $6,000 gross monthly income with $400 of other debts, the front-end limit is 0.28 × 6,000 = $1,680 and the back-end limit is 0.36 × 6,000 − 400 = $1,760, so the binding figure is the lower one, $1,680. At 6% over 30 years that payment supports a loan of $280,210; adding a $40,000 down payment gives a maximum home price of $320,210.
Assumptions, rounding, and limitations
Assumptions
- Gross annual income is divided by 12 to get gross monthly income, before tax and other deductions.
- The affordable payment is min(0.28 × gross monthly income, 0.36 × gross monthly income − other monthly debt payments), floored at zero.
- That payment is treated as a fully amortizing, fixed-rate principal-and-interest payment over the entered term, and inverted with the standard annuity present-value formula to obtain the maximum loan.
- Maximum home price is the maximum loan plus the entered down payment, which assumes the whole down payment is applied to price rather than to closing costs.
Rounding: All intermediate values retain full floating-point precision; displayed currency amounts are rounded to the nearest whole unit for presentation only.
Limitations
- Excludes property tax, homeowners insurance, HOA dues, mortgage insurance and closing costs, all of which reduce real affordability. The result is therefore an upper bound.
- 28/36 is a budgeting convention, not an underwriting standard. Published lender maximums are higher — up to 45% or 50% total DTI under Fannie Mae rules — so this figure is intentionally conservative.
- It does not assess credit score, employment history, reserves, property type or loan program, all of which affect what you can actually borrow.
- A fixed rate is assumed for the full term. Adjustable-rate products, buydowns and points are not modelled.
- This is general information for planning, not a pre-qualification, a lending decision, or financial advice.
Sources
- Selling Guide B3-6-02: Debt-to-Income Ratios — Fannie Mae
- Qualified Mortgage Definition under the Truth in Lending Act (Regulation Z): General QM Loan Definition — Consumer Financial Protection Bureau
- What is a debt-to-income ratio? — Consumer Financial Protection Bureau
The 28/36 guideline this calculator applies
The guideline holds that housing costs should stay under 28% of gross monthly income (the 'front-end' ratio) and that total debt payments — housing plus car, cards and loans — should stay under 36% (the 'back-end' ratio).
This calculator takes the lower of those two limits to find a monthly payment, then inverts the standard annuity formula to reach the maximum loan, and adds your down payment for a maximum home price. Paying down other debts or saving a larger deposit both raise the result.
28/36 is a budgeting convention, not a lending limit
It is worth being precise about where 28/36 comes from, because it is often described as the rule lenders apply. It is not. It is a long-standing personal-finance convention, and real underwriting standards are looser.
Fannie Mae's Selling Guide sets a maximum total DTI of 36% for manually underwritten loans but permits up to 45% when credit-score and reserve requirements are met, and up to 50% for casefiles run through Desktop Underwriter. Separately, the CFPB's General QM Final Rule removed the old 43% DTI limit entirely and replaced it with price-based thresholds.
The practical consequence is that a lender may well approve you for more than this calculator shows. That gap is intentional. The figure here is what fits a conservative budget, not the ceiling of what someone will lend you.
What the estimate excludes
The payment modelled here is principal and interest only. Property tax, homeowners insurance, HOA dues and mortgage insurance are real recurring housing costs, and lenders count them inside the front-end ratio even though this tool does not.
Because those costs are excluded, the maximum home price shown is an upper bound. In markets with high property taxes or HOA fees the realistic figure can be materially lower, so leave headroom rather than treating the output as a target.
Frequently asked questions
▶How much house can I afford on my salary?
It depends on your other debts, down payment and interest rate — not income alone. Enter your details above for a personalised estimate based on standard 28/36 lending ratios.
▶Should I borrow the maximum I'm approved for?
Usually not. The maximum a lender allows can leave your budget stretched. Borrowing below your ceiling gives you room for emergencies, tax, insurance and life.
▶What is the 28/36 rule?
It's a budgeting convention: housing costs stay under 28% of gross monthly income (the front-end ratio) and all debt payments combined stay under 36% (the back-end ratio). This calculator uses the lower of the two. Note that it is a personal-finance guideline rather than an underwriting standard — Fannie Mae permits up to 45% total DTI manually and 50% through Desktop Underwriter, so a lender may approve more than this shows.
▶How does my down payment affect affordability?
A bigger deposit means you borrow less for the same home, or can afford a pricier home for the same monthly payment. It can also unlock a lower interest rate and help you avoid mortgage insurance.
▶Do my other debts reduce how much I can borrow?
Yes. Car loans, credit-card minimums and student loans all count towards the 36% back-end limit, leaving less room for housing. Paying them down before you apply raises the home price you can afford.
▶Does a higher interest rate lower the price I can afford?
Yes. A higher rate means a larger share of each payment goes to interest, so the same affordable monthly payment supports a smaller loan — and therefore a lower home price.
Learn more
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Open calculator →Disclaimer: Mortgage Affordability Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.