Mortgage Affordability Calculator
About Mortgage Affordability Calculator
What Affordability Really Measures
Affordability is not a single number printed on a listing. It is the largest home price your income can support after every recurring cost of owning that home is accounted for. A monthly mortgage payment is only the visible part. Property taxes, homeowners insurance, private mortgage insurance, and homeowners association dues all draw from the same paycheck, and lenders look at the whole bundle when they decide how much to lend.
This calculator starts from your income and works backward. Rather than asking “what does this house cost each month?” it asks “given the payment I can comfortably carry, how expensive a home does that payment buy?” That reversal is what makes an affordability tool different from a standard payment calculator. It treats your budget as the fixed input and solves for the price, the loan amount, and the full payment breakdown that fit inside it.
The result is a planning figure, not a guarantee. It mirrors the ratios most underwriters use, so it lands close to a real pre-approval for many buyers. But credit score, cash reserves, employment history, and the specific loan program all shift the final number. Use the estimate to set the price range for your search, then confirm it with a lender before you make offers.
The 28/36 Rule and Debt-to-Income Ratios
Lenders measure risk with two debt-to-income (DTI) ratios. The 28/36 rule is the long-standing rule of thumb that sets a sensible default for both.
- Front-end ratio (28%): Your total monthly housing payment, including principal, interest, taxes, insurance, HOA, and PMI, should sit at or below 28% of your gross monthly income.
- Back-end ratio (36%): All of your monthly debt payments combined, housing plus car loans, student loans, and minimum credit card payments, should sit at or below 36% of gross monthly income.
Your affordable housing payment is the smaller of those two limits. When you carry little other debt, the 28% front-end limit usually governs. When you carry significant monthly obligations, the 36% back-end limit kicks in earlier and becomes the binding constraint, which is why the result card tells you which ratio is holding your budget down. Many loan programs allow higher figures, so both limits are editable; FHA loans, for instance, often stretch to 31/43 or beyond with compensating factors.
How the Math Works
The calculation runs in three steps. First, it converts your gross annual income to a monthly figure and applies both DTI limits to produce two budgets: the front-end budget and the back-end budget after subtracting your existing monthly debts. The smaller of the two becomes your monthly housing budget.
Second, it has to translate that monthly budget into a home price, and here is the wrinkle: two of the costs depend on the price itself. Property tax is a percentage of the home value, and PMI depends on your loan-to-value ratio, which also depends on the price. A simple formula cannot solve this cleanly, so the calculator iterates. It repeatedly tests a candidate price, computes the full payment that price would require, and narrows the range until it finds the highest price whose total payment still fits inside your budget. This binary search converges on a precise answer in a fraction of a second.
Third, it reports the maximum home price, the loan amount once your down payment is subtracted, and a line-by-line breakdown of the monthly payment so you can see exactly where the money goes. The principal and interest portion uses the standard amortization formula, the same one behind the mortgage payment calculator if you want to model a specific loan in more detail.
Every Input, Explained
- Gross annual income: Your pre-tax income from all reliable sources. Use gross rather than take-home because lenders underwrite on gross figures.
- Monthly debt payments: The recurring minimums lenders count, such as auto loans, student loans, and credit card minimums. To plan a payoff before you buy, the debt payoff calculator shows how fast you can clear them.
- Down payment / cash: The cash you will put toward the purchase. It is subtracted from the price to set the loan amount and decides whether PMI applies. Use the down payment calculator to plan how long it takes to save a target amount.
- Interest rate and term: The annual rate and the length of the loan, typically 30 or 15 years. A lower rate or longer term lowers the monthly payment and raises the price your budget supports.
- Property tax rate: The annual tax as a percent of home value; it varies widely by location. The property tax calculator helps you estimate the rate for a specific area.
- Home insurance, HOA, and PMI rate: Annual insurance in dollars, monthly HOA dues, and the PMI rate applied whenever your down payment is under 20%.
- Front-end and back-end DTI limits: Editable so you can match a specific loan program or test a more conservative target than 28/36.
A Worked Example
Suppose you earn $96,000 a year, which is $8,000 a month gross. You pay $450 a month toward a car loan and student loans, and you have $60,000 saved. Rates are 6.5% on a 30-year loan, the local property tax rate is 1.1%, insurance runs $1,800 a year, there are no HOA dues, and PMI would cost 0.6%.
The front-end limit is 28% of $8,000, or $2,240. The back-end limit is 36% of $8,000 minus $450 of existing debt, or $2,430. Because the front-end figure is smaller, your housing budget is $2,240 a month, and the front-end ratio is the binding constraint. The calculator then searches for the price whose full payment, taxes, insurance, and PMI included, lands at that $2,240 ceiling. With a $60,000 down payment that works out to a home price in the high $300,000s.
Now pay off that $450 of debt before applying. The back-end limit jumps to $2,880, but the front-end limit is unchanged at $2,240, so your budget barely moves. The lesson is that when the front-end ratio binds, extra income or a larger down payment moves your budget more than clearing small debts. When the back-end ratio binds, the opposite is true and paying down debt is the fastest lever.
Ways to Raise Your Affordable Budget
- Increase your down payment. More cash lowers the loan, and crossing the 20% threshold removes PMI, which frees up part of your monthly budget for principal and interest.
- Pay down monthly debt. This only helps when the back-end ratio is the limiting factor, but in that case it is often the single most effective move.
- Improve your interest rate. A stronger credit score or buying points lowers the rate, which lowers the payment and raises the supportable price.
- Choose a different term. A 30-year loan has a lower payment than a 15-year loan for the same balance, raising affordability at the cost of more lifetime interest.
- Shop tax and insurance costs. Property tax and insurance differ sharply by location and provider, and lower carrying costs leave more room for principal and interest.
Where This Fits in Your Buying Plan
Affordability is the first checkpoint, not the last. Once you know your price range, the next questions are whether buying beats renting for your timeline and how much cash you need at closing. To compare the long-run cost of owning against staying a renter, run the numbers through the rent vs. buy calculator, which weighs ownership costs, equity, and investment returns side by side.
When you settle on a target price, switch to the mortgage calculator to model the exact loan, including extra payments and escrow, and use the down payment calculator to set a savings timeline for the cash you need. Treating these tools as a sequence, affordability first, then rent-versus-buy, then loan and down payment, turns a vague budget into a concrete, defensible plan you can take to a lender.
Above all, remember that the maximum here is a ceiling, not a target. Qualifying for a payment does not make it comfortable. Maintenance, utilities, and an emergency fund all compete for the same income, so many buyers deliberately aim for a payment below their maximum to keep their budget resilient against rate changes, repairs, and life.
Frequently Asked Questions
How much house can I afford on my income?
A common starting point is the 28/36 rule. Lenders typically want your total housing payment to stay at or below 28% of your gross monthly income, and all of your monthly debt payments combined (housing plus car loans, student loans, and minimum credit card payments) to stay at or below 36%. This calculator applies both limits, takes the lower of the two as your housing budget, and then works backward through your interest rate, term, taxes, insurance, HOA dues, and PMI to estimate the home price that budget supports.
What is the 28/36 rule?
The 28/36 rule is a guideline for two debt-to-income (DTI) ratios. The front-end ratio (28%) caps your monthly housing payment as a share of gross income. The back-end ratio (36%) caps all recurring debt payments combined. For example, on $7,000 of gross monthly income the front-end limit is $1,960 and the back-end limit is $2,520 minus your existing debts. Your affordable housing payment is the smaller of those two numbers. Many loan programs allow higher ratios, so the calculator lets you adjust both limits.
Does the calculator include property taxes, insurance, and PMI?
Yes. The estimate solves for your full PITI payment (principal, interest, taxes, and insurance) plus HOA dues and private mortgage insurance (PMI). Property tax is estimated from the home price using the annual rate you enter, homeowners insurance is an annual dollar figure, HOA is a monthly amount, and PMI is added whenever your loan-to-value ratio is above 80% (meaning your down payment is under 20%). Because taxes and PMI depend on the home price, the calculator iterates to find the price where every cost fits inside your budget.
How does my down payment change what I can afford?
Your down payment does two things. It is added directly to the loan amount to set the maximum home price, and it determines whether you pay PMI. A down payment of 20% or more removes PMI, freeing up part of your monthly budget for a larger loan. A smaller down payment means you both borrow against less cash and carry PMI, which lowers the price your monthly budget supports. Try a few down payment figures to see how the trade-off plays out for your situation.
Why is my back-end ratio limiting my budget?
If you carry meaningful monthly debt such as car loans, student loans, or credit card minimums, those payments count against the 36% back-end limit but not the 28% front-end limit. When debts are high, the back-end calculation produces a smaller housing budget, so it becomes the binding constraint. Paying down or paying off those debts before you apply can raise the housing payment you qualify for, sometimes by more than increasing your income would.
Is the affordable amount the same as what a lender will approve?
Not exactly. This calculator gives a well-grounded estimate using standard underwriting ratios, but a lender also weighs your credit score, employment history, cash reserves, the specific loan program, and current rates. Conventional, FHA, VA, and USDA loans each use different limits and insurance rules. Treat the result as a planning figure to set your search range, then get a pre-approval for a number you can rely on when making offers.
Should I borrow the maximum amount I qualify for?
Qualifying for a payment is not the same as it being comfortable. The maximum result here is an underwriting ceiling, not a recommendation. Maintenance, utilities, repairs, and an emergency fund all compete for the same paycheck, and buying at your absolute limit leaves little room for those costs or for income changes. Many buyers deliberately target a payment below the maximum so their budget stays flexible.