Mortgage Affordability Calculator
Find the maximum home price you can afford based on income, existing debts, down payment, mortgage rate, and the standard 28/36 housing-cost rules. Includes property tax and insurance in the math.
Max affordable home price
$330,350
Max monthly housing payment (PITI)
$2,240
Monthly mortgage factor (per $1 borrowed)
0.01
Max loan amount
$280,350
Monthly principal & interest
$1,772
Monthly property tax + insurance
$468
Housing-cost share of income (front-end DTI)
28.0%
Total debt share of income (back-end DTI)
34.3%
Max Home Price by Loan Term Length
How to read your result
The 'Max affordable home price' is the headline number — the largest sticker price your income, debts, and down payment can support while keeping the total housing payment within the 28/36 rule. It already deducts property tax and insurance from your monthly housing budget, so the principal-and-interest portion is what's left for the actual loan.
'Max monthly housing payment (PITI)' is the lower of two limits: 28% of gross income (the front-end rule) or your DTI cap minus existing debts (the back-end rule). Whichever is more restrictive wins. If you have meaningful existing debt (car loan, student loans), the back-end rule will usually be tighter.
'Front-end DTI' shows the share of gross income going to the entire housing payment (P&I + tax + insurance). The standard target is 28% — the calculator solves for the price that lands at or below that line. 'Back-end DTI' adds your existing debts on top and is capped at the value you set (default 36%).
The chart shows how max home price changes with loan term. Stretching from 15 years to 30 years roughly doubles affordable price for the same monthly payment — but at the cost of paying nearly twice the lifetime interest. Use it to see the trade-off in concrete dollars.
When to use this tool
- ›Setting an upper limit on home shopping before you start touring open houses or talking to lenders. Plug in conservative numbers and treat the output as a ceiling, not a target.
- ›Sanity-checking a pre-approval letter. Lenders sometimes approve borrowers up to 43–50% back-end DTI; this calculator's 36% default keeps you in safer territory.
- ›Comparing how down-payment levels move the affordable-price ceiling. Doubling the down payment from $50k to $100k typically increases max home price by less than the down-payment delta itself, because the bigger constraint is monthly cash flow.
- ›Stress-testing affordability against a higher rate environment. Run the calculator at today's rate, then re-run at +1.5 points to see how much your buying power shrinks if rates climb during your search.
Methodology
The calculator applies the conventional 28/36 rule: max housing cost ≤ 28% of gross monthly income (front-end), and total debt ≤ 36% of gross monthly income (back-end). The DTI cap is configurable — Fannie Mae and FHA loans sometimes allow higher back-end ratios.
Property tax and homeowners insurance are entered as annual percentages of home value, not flat dollar amounts. This makes the math self-consistent: a higher home price implies higher tax and insurance, which the calculator solves for simultaneously rather than approximating.
The monthly P&I formula is the standard fixed-rate amortization equation: payment = loan × r / (1 − (1 + r)^(−n)), where r = annual_rate / 12 / 100 and n = months. At a 0% rate the formula simplifies to loan / months.
Limits we acknowledge: this calculator does not model PMI (typical for under 20% down — adds roughly 0.5–1.5% of loan annually), HOA fees, ARM rate adjustments, or jumbo-loan limits. It also assumes a fixed gross income; variable or commission income usually gets multiplied by a discount factor (often ~0.75) by lenders. For a payment-only view of a specific loan amount, see /tools/loan-amortization/.
Site-wide methodology framework: /methodology/ · Pre-publication standards: /editorial-standards/
FAQ
Why does the calculator use the 28/36 rule and not what my lender quoted me?
The 28/36 rule is the conservative-conventional benchmark that's been the industry standard for decades. Lenders may approve up to 43% back-end DTI (and FHA goes higher), but spending that share of pre-tax income on debt typically leaves households cash-strapped against unexpected expenses. You can raise the DTI cap input if you want to see what a more aggressive lender would approve — just understand that the higher numbers are budget-stress territory, not safe-zone.
Should I use my pre-tax or after-tax income?
Pre-tax (gross). All standard lender calculations and the 28/36 rule are based on gross income. After-tax dollars are what you actually keep, but the industry conventions you're being measured against assume pre-tax. If you want a more conservative personal sanity check, use 28% of after-tax income as your ceiling — that's a stricter test than the lender will apply.
What counts as 'existing monthly debt'?
Minimum required payments on car loans, student loans, credit cards, personal loans, and any other revolving or installment debt. Do not include rent (it disappears once you buy), utilities, groceries, or discretionary spending — those aren't part of the DTI calculation. If you carry credit-card balances, use the minimum payment, not the full balance.
Does this calculator account for PMI?
No. PMI (private mortgage insurance) typically applies when your down payment is under 20% and adds roughly 0.5–1.5% of the loan amount annually. To approximate, raise the 'insurance rate' input by your expected PMI percentage. Example: 0.5% homeowners insurance + 0.8% PMI = 1.3%. PMI usually drops off automatically when you hit 22% equity (or 20% on request) so the higher number is temporary, not a 30-year cost.
Why does adding 1 point to the interest rate cut my affordable price so much?
Because at typical mortgage rates, the monthly payment is mostly interest. A 1-point rate increase on a $400k loan adds roughly $250–300 to the monthly payment. To stay within your 28% income cap, the loan amount has to shrink by about 10–12% — and your max home price drops by the loan reduction (down payment is fixed). This is why timing and rate shopping matter so much in a mortgage.
What's the difference between this and the loan amortization calculator?
This tool answers 'what's the most I can afford?' given your income and constraints. The Loan Amortization Calculator answers 'for a given loan amount, what's the monthly payment and total interest?' Use this one first to set a price ceiling; use loan-amortization to model the specific loan once you've narrowed in on a price.
Why is my front-end DTI in the result less than 28%?
Because the back-end DTI rule was the binding constraint. If your existing debts are high enough, the dtiCap minus debts (the back-end rule) becomes the lower of the two limits, which means the resulting front-end DTI ends up below 28%. This is the calculator's way of saying: your existing debt load is what's limiting your home-buying budget, not the housing-cost ratio itself.