The 28/36 rule gives you a starting point, but your real limit depends on your debt and down payment
Most lenders use the 28/36 rule as a baseline: your monthly housing payment (mortgage, property tax, insurance, and homeowners association fees) should not exceed 28% of your gross monthly income, and your total debt payments should not exceed 36%. If you earn $5,000 a month before taxes, that means a housing payment around $1,400 is the upper limit most lenders will consider. But this rule is a floor for qualification, not a ceiling for what you can actually afford to live on.
Your real affordability depends on three things: how much you have saved for a down payment, what other debts you carry, and what your actual monthly expenses look like after housing. A lender may approve you for a $400,000 house, but that does not mean you can comfortably pay for it alongside groceries, utilities, childcare, and car insurance.
Key Takeaways
- The 28/36 rule is what lenders use to decide whether to approve you, not what you can afford to live on comfortably.
- Your down payment size directly affects your monthly payment: a 20% down payment means a lower mortgage than a 3% down payment on the same house.
- Other debts—car loans, student loans, credit cards—reduce the housing payment a lender will approve, even if your income is high.
- Your actual monthly expenses (food, utilities, insurance, childcare, transportation) must fit alongside your housing payment, which the 28/36 rule does not account for.
- A mortgage calculator can show you the payment on a specific loan amount, but only your own budget can tell you whether that payment leaves room for the rest of your life.
How lenders calculate what they will approve
When you explore for a mortgage, the lender runs your income and debts through the 28/36 formula. They pull your credit report, which lists every car loan, student loan, credit card balance, and other payment you make each month. They add up all those payments and subtract them from your gross income. What remains is what they think you can spend on housing.
If you earn $5,000 a month and already pay $800 in car and student loans, the lender sees $4,200 left. Thirty-six percent of $5,000 is $1,800, but you are already at $800, so they may approve you for a housing payment of $1,000 instead. The debt you already carry shrinks the house you can afford, even if your income is high.
The down payment you bring also matters. A 20% down payment on a $300,000 house means you borrow $240,000. A 3% down payment on the same house means you borrow $291,000. The second loan carries a higher monthly payment, a higher interest rate (because the lender takes more risk), and mortgage insurance on top. The same house costs you $200 to $300 more per month depending on how much you put down.
The gap between what lenders approve and what you can afford
Lenders do not know your grocery budget, your childcare costs, or whether you have a car that needs replacing soon. The 28/36 rule assumes you have no other major expenses, which is not how life works. A housing payment that passes the 28/36 test can still leave you unable to save, pay for emergencies, or cover the actual cost of owning a home.
Homeownership costs more than the mortgage payment. Property taxes vary by location but often run $100 to $300 per month on a $300,000 house. Homeowners insurance is typically $80 to $150 per month. Maintenance and repairs average 1% of the home's value per year—on a $300,000 house, that is $250 per month. If the house is in a planned community, homeowners association fees can add another $100 to $500 per month. A lender includes taxes and insurance in the housing payment calculation, but maintenance is on you.
Add in utilities (which are often higher in a house than an apartment), yard work, appliance replacement, and roof repairs, and the true cost of housing is 30% to 40% higher than the mortgage payment alone. If a lender approves you for $1,400 a month, the real monthly cost of that house may be closer to $1,800 or $1,900.
How to find your actual affordability number
Start with your take-home pay—the amount that actually hits your bank account after taxes, not your gross income. If you earn $5,000 gross but take home $3,600 after federal and state taxes, that is the number you budget from.
List every monthly expense: food, utilities, insurance (car, health, life), childcare, transportation, phone, internet, subscriptions, debt payments, and savings. Most people find they spend $2,000 to $3,000 per month on non-housing expenses. Subtract that from your take-home pay. What remains is what you can actually spend on housing and still have a buffer for emergencies.
If you take home $3,600 and spend $2,000 on everything else, you have $1,600 left for housing. But you should not spend all of it. Financial advisors typically recommend keeping 10% to 20% of your take-home pay as a monthly buffer for unexpected costs—car repairs, medical bills, job loss. If you keep $360 as a buffer, your real housing budget is $1,240, not the $1,400 a lender might approve.
Use a mortgage calculator to see what loan amount produces a payment in your range. Most calculators let you enter the loan amount, interest rate, and loan term (usually 15 or 30 years) and show you the monthly payment. You can work backward: enter different loan amounts until the payment matches your budget.
What your down payment size means for monthly cost
The larger your down payment, the smaller your monthly payment and the lower your interest rate. Lenders offer better rates to borrowers who put down 20% or more because the lender's risk is lower. Here is how the math works on a $300,000 house at a 7% interest rate over 30 years:
| Down Payment | Loan Amount | Monthly Payment (Principal + Interest) | Mortgage Insurance | Total Monthly Cost |
|---|---|---|---|---|
| 3% ($9,000) | $291,000 | $1,938 | $145 | $2,083 |
| 10% ($30,000) | $270,000 | $1,797 | $68 | $1,865 |
| 20% ($60,000) | $240,000 | $1,597 | $0 | $1,597 |
The difference between a 3% and 20% down payment is nearly $500 per month on the same house. If you are deciding between houses you can afford, a larger down payment gives you more breathing room in your monthly budget. If you are deciding how much house to buy, a smaller down payment means you need to buy a less expensive house to stay within your budget.
How to adjust if the approved amount feels too high
If a lender approves you for $1,500 a month but your budget says $1,000, trust your budget. Lenders are in the business of lending; they benefit when you borrow more. Your budget is built on your actual life.
You have three levers to pull. First, save more for a down payment. Every additional percentage point you put down reduces your monthly payment and removes mortgage insurance. Saving an extra $10,000 to $15,000 can lower your payment by $100 to $150 per month.
Second, pay down other debts before you buy. If you have $300 in car and student loan payments, paying off the car loan before you explore for a mortgage frees up $300 per month for housing. This is one of the few times paying off debt before a major purchase makes financial sense.
Third, look at less expensive houses. A $250,000 house instead of a $350,000 house is not a failure; it is a realistic choice based on your income and expenses. You can always buy a more expensive house later when your income rises or your other debts are gone.
What happens if you stretch beyond your budget
People who buy houses at the top of their approved range often face one of three outcomes. Some manage it by cutting other expenses—no vacations, minimal dining out, delayed car replacement—and live under constant financial stress. Some experience a job loss, medical emergency, or other income disruption and fall behind on the mortgage. Some sell the house within five years because they realize they cannot afford it and want their life back.
A mortgage is a 30-year commitment. Your income may rise, but it may also fall. Your expenses may drop, but they may also increase—a child, an illness, an aging parent. A house payment that leaves no room for those changes is a house payment you cannot actually afford.
Frequently Asked Questions
What interest rate should I assume when calculating affordability?
Use the current rate for a 30-year fixed mortgage in your area. Rates change weekly, so check your local lenders' websites or a mortgage rate tracker. If rates are currently 7%, use 7%. Do not assume rates will drop; if they do, you can refinance later and lower your payment.
Should I include property taxes and insurance in my affordability calculation?
Yes. Property taxes vary by location and home value, but they typically run 0.5% to 1.5% of the home's value per year. Insurance runs $800 to $1,800 per year depending on location and home value. Add both to your monthly payment estimate. A mortgage calculator that includes taxes and insurance will do this automatically.
Does the 28/36 rule account for childcare or student loan payments?
The 36% part does account for other debts like student loans and car payments. It does not account for childcare, which is why the rule is a floor, not a ceiling. If you pay $1,200 per month for childcare, that comes out of your take-home pay before you calculate what you can spend on housing.
What if I have irregular income or work freelance?
Lenders typically average your income over the past two years and may require higher down payments or charge higher interest rates. For your own affordability calculation, use your lowest recent year of income, not your best year. This gives you a conservative number that you can actually hit in slower months.
Can I afford a house if I have student loan debt?
Yes, but the student loan payment reduces the housing payment a lender will approve. If you have $300 in monthly student loan payments, a lender will subtract that from what they think you can spend on housing. You can still buy a house; it will just be a less expensive one than someone with the same income but no student debt.