# How to Calculate Your Mortgage Affordability: Rules, Ratios, and 2026 Limits By Opendoor Editorial Team | 2025-11-28 > Calculate your mortgage affordability: a complete guide Figuring out how much mortgage you can afford is one of the most important — and most stressful — steps in the homebuying journey. Borrow too much and you risk financial strain for decades. Borrow too little and you might miss out on the right home. This mortgage affordability calculator guide gives you everything you need to calculate mortgage affordability with confidence: proven rules of thumb, formula breakdowns, worked examples at four different income levels, and a clear framework for deciding what truly fits your budget. Whether you're a first-time buyer or moving up, you'll walk away knowing exactly how much house you can afford. [Get your offer](#) ## How to Use a Mortgage Affordability Calculator A mortgage affordability calculator takes your financial inputs and estimates the maximum loan — and home price — you can reasonably afford. Below is a step-by-step walkthrough you can follow manually or use alongside any online calculator tool. **Inputs you'll need:** | **Input** | **Where to Find It** | | Gross annual income (pre-tax) | Pay stubs or tax return | | Monthly debt payments | Credit card minimums, auto loans, student loans | | Down payment amount | Savings earmarked for purchase | | Estimated interest rate | Current lender quotes or Freddie Mac's [Primary Mortgage Market Survey](https://www.freddiemac.com/pmms) | | Loan term | Typically 30 or 15 years | | Estimated property tax rate | County assessor website | | Homeowners insurance estimate | Insurance quote or local average | ### Step 1 — Determine Your Gross Monthly Income Start with your **gross monthly income** — that's your total pre-tax earnings divided by 12. If you earn a $100,000 annual salary, your gross monthly income is **$8,333**. Include all stable, documentable income sources: - **Base salary or hourly wages** - **Bonuses and commissions** (lenders typically average the past two years) - **Self-employment income** (net profit from Schedule C or K-1) - **Rental income, alimony, or investment income** (if consistent) > **Tip:** Lenders use gross income, not net. But when deciding what you're personally comfortable paying, thinking in terms of take-home pay gives you a more realistic picture. ### Step 2 — Calculate Your Monthly Debts List every recurring monthly debt obligation that shows up on your credit report: - Minimum credit card payments - Auto loan or lease payments - Student loan payments (even if in deferment — lenders may use 0.5%–1% of the balance) - Personal loans - Child support or alimony **Do not include** utilities, groceries, subscriptions, or other living expenses — lenders don't factor those into debt-to-income calculations, though you absolutely should when budgeting. ### Step 3 — Apply the 28/36 Rule The **28/36 rule** is the most widely used mortgage affordability rule of thumb. It sets two spending ceilings: - **28%** of gross monthly income for housing costs (your front-end ratio) - **36%** of gross monthly income for all debt payments combined, including housing (your back-end ratio) We break both ratios down in detail in the sections below. For now, multiply your gross monthly income by 0.28 to find your maximum housing payment, and by 0.36 to find your total allowable debt load. **Example:** $8,333 gross monthly income × 0.28 = **$2,333 max housing payment** ### Step 4 — Factor in Your Down Payment Your down payment directly affects how much you need to borrow — and whether you'll pay private mortgage insurance (PMI). A larger down payment means a smaller loan and lower monthly payments. - **20% down** eliminates PMI and gives you instant equity. - **10% down** is a common middle ground. - **3%–5% down** is possible with conventional and FHA loans, though PMI will add to your monthly costs. Learn more about whether [5% is enough for a down payment](https://www.opendoor.com/articles/briefs/is-5-percent-enough-down-payment). According to the [National Association of Realtors' 2024 Profile of Home Buyers and Sellers](https://www.nar.realtor/research-and-statistics/research-reports/highlights-from-the-profile-of-home-buyers-and-sellers), the median down payment for first-time buyers was 8%, while repeat buyers put down a median of 19%. For a detailed look at all the upfront costs, see our guide on [how much to save for a house down payment](https://www.opendoor.com/articles/how-much-to-save-for-house). ### Step 5 — Account for Interest Rate and Loan Term Even a small difference in your interest rate dramatically changes what you can afford. | **Loan Amount** | **Rate** | **Term** | **Monthly P&I Payment** | | $350,000 | 6.5% | 30 years | $2,212 | | $350,000 | 7.0% | 30 years | $2,329 | | $350,000 | 7.5% | 30 years | $2,447 | | $350,000 | 6.5% | 15 years | $3,049 | A half-point rate increase on a $350,000 loan adds roughly **$117/month** — or over **$42,000** over the life of a 30-year mortgage. Locking in the lowest rate you qualify for is one of the most powerful levers in mortgage affordability. ## The 28% Rule: Your Front-End Ratio Explained The **28% rule mortgage** guideline states that your total monthly housing costs should not exceed **28% of your gross monthly income**. This is also called your **front-end ratio** because it only looks at housing expenses — the "front" of your debt picture. ### What Counts as "Housing Costs" Your front-end ratio includes your full **PITI payment**: - **P**rincipal - **I**nterest - **T**axes (property taxes) - **I**nsurance (homeowners insurance) It also includes **PMI** (if applicable) and **HOA dues**. ### The Formula > **Front-end ratio = Total monthly housing costs ÷ Gross monthly income** To find your maximum housing payment: > **Maximum housing payment = Gross monthly income × 0.28** ### Worked Example - **Gross annual income:** $90,000 - **Gross monthly income:** $7,500 - **Maximum housing payment (28% rule):** $7,500 × 0.28 = **$2,100/month** That $2,100 must cover principal, interest, taxes, insurance, PMI, and HOA fees — not just the mortgage payment you see advertised. ### When the 28% Rule Works — and When It Doesn't **It works well when:** - You have moderate non-housing debt - You live in an area with average cost of living - You want a conservative, safe spending target **It breaks down when:** - You live in a high-cost market where 28% won't buy a livable home - You have zero other debts (you may be able to safely spend more on housing) - You have very high non-housing obligations (28% on housing may still leave you overextended) The 28% rule is a starting point, not a final answer. Pair it with the back-end ratio below for a fuller picture. ## The 36% Rule: Your Back-End DTI Ratio Explained The **36% rule** addresses your **back-end ratio** — your **total DTI (debt-to-income) ratio**, which includes housing costs *plus* all other monthly debt obligations. Understanding the difference between the front-end ratio and back-end ratio is essential for accurately gauging mortgage affordability. ### The Formula > **Back-end DTI ratio = (Total monthly housing costs + All other monthly debts) ÷ Gross monthly income** According to the [Consumer Financial Protection Bureau (CFPB)](https://www.consumerfinance.gov/ask-cfpb/what-is-a-debt-to-income-ratio-en-1791/), most lenders prefer a back-end DTI ratio of **36% or lower** for conventional loans, though many will approve borrowers up to 43%, and [FHA loans](https://www.hud.gov/buying/loans) may accept DTI ratios as high as 50% with compensating factors. ### How It Differs From the 28% Rule | | **Front-End Ratio (28% Rule)** | **Back-End Ratio (36% Rule)** | | **What it measures** | Housing costs only | All debts, including housing | | **Target ceiling** | 28% of gross income | 36% of gross income | | **Debts included** | PITI + PMI + HOA | PITI + PMI + HOA + car loans, student loans, credit cards, etc. | | **Purpose** | Ensures housing is affordable in isolation | Ensures total debt load is manageable | ### Worked Example - **Gross monthly income:** $7,500 - **Monthly housing payment:** $2,100 - **Car loan:** $350/month - **Student loans:** $200/month - **Credit card minimums:** $100/month - **Total monthly debts:** $2,100 + $350 + $200 + $100 = **$2,750** - **Back-end DTI:** $2,750 ÷ $7,500 = **36.7%** This borrower is just above the 36% threshold. A lender using conventional guidelines might still approve the loan, but the borrower should evaluate whether there's enough breathing room for savings, emergencies, and daily living. If you're working through [how much it costs to buy a house](https://www.opendoor.com/articles/how-much-does-it-cost-to-buy-a-house), DTI is the single most important number to understand. ## Mortgage Affordability Rules of Thumb Compared There's no single "right" way to calculate mortgage affordability. Here's how the most common rules of thumb stack up: | **Rule** | **What It Says** | **Formula** | **Best For** | | **28% Rule** (Front-End) | Housing costs ≤ 28% of gross income | Gross monthly income × 0.28 | Conservative housing budget ceiling | | **36% Rule** (Back-End) | Total debt ≤ 36% of gross income | (All monthly debts) ÷ gross income ≤ 0.36 | Full debt-load check | | **28/36 Rule** (Combined) | Housing ≤ 28% *and* total debt ≤ 36% | Both formulas applied together | The most widely recommended standard | | **3× Annual Income** | Home price ≤ 3× gross annual income | Annual income × 3 | Quick back-of-napkin estimate | | **4–5× Annual Income** | Home price ≤ 4–5× gross income | Annual income × 4 or 5 | Higher-income or low-debt buyers | | **35/45 Model** | Housing 35% of after-tax income; total debt 45% | Uses net income, not gross | Buyers who want a lifestyle-adjusted view | > **Bottom line:** The **28/36 rule** remains the gold standard because it checks both housing costs and total debt. If you're looking for a quick "how much house can I afford" rule of thumb, multiply your annual income by 3 for a conservative estimate, or by 4–5 if you have minimal debt and a strong down payment. ## How Much Mortgage Can I Afford? Examples by Income Level The question "how much mortgage can I afford?" depends on your full financial picture — but real numbers help. Below are worked examples at four income levels using these shared assumptions: **Assumptions for all examples:** - 30-year fixed mortgage at **6.75% interest rate** - **10% down payment** - Property tax rate: **1.1% of home value annually** - Homeowners insurance: **$1,800/year** - PMI: **0.5% of loan amount annually** (since down payment < 20%) - 28/36 rule applied - Monthly non-housing debts are listed per scenario ### Mortgage Affordability on a $50,000 Salary | **Metric** | **Value** | | Gross monthly income | $4,167 | | Max housing payment (28%) | $1,167 | | Non-housing debts assumed | $250/month | | Max total debt (36%) | $1,500 | | Estimated max home price | **~$165,000** | | Estimated mortgage amount | ~$148,500 | At this income, budget-consciousness is critical. Every dollar counts — make sure to account for [closing costs](https://www.opendoor.com/articles/how-much-are-closing-costs-for-seller) and moving expenses beyond the down payment itself. ### Mortgage Affordability on a $75,000 Salary | **Metric** | **Value** | | Gross monthly income | $6,250 | | Max housing payment (28%) | $1,750 | | Non-housing debts assumed | $400/month | | Max total debt (36%) | $2,250 | | Estimated max home price | **~$255,000** | | Estimated mortgage amount | ~$229,500 | This income bracket opens the door to many starter homes in mid-range markets. If you're beginning your search, our [open house tips for first-time buyers](https://www.opendoor.com/articles/open-house-tips-for-first-time-buyers) can help you make the most of every visit. ### Mortgage Affordability on a $100,000 Salary | **Metric** | **Value** | | Gross monthly income | $8,333 | | Max housing payment (28%) | $2,333 | | Non-housing debts assumed | $500/month | | Max total debt (36%) | $3,000 | | Estimated max home price | **~$345,000** | | Estimated mortgage amount | ~$310,500 | A six-figure salary gives you meaningful purchasing power in most U.S. markets. With a higher down payment or lower debts, you could push that ceiling above $375,000–$400,000. ### Mortgage Affordability on a $150,000 Salary | **Metric** | **Value** | | Gross monthly income | $12,500 | | Max housing payment (28%) | $3,500 | | Non-housing debts assumed | $700/month | | Max total debt (36%) | $4,500 | | Estimated max home price | **~$525,000** | | Estimated mortgage amount | ~$472,500 | At this level, the difference between 10% and 20% down is significant — a 20% down payment eliminates PMI and could boost your maximum home price to roughly $575,000 or more. ### Summary Table | **Annual Income** | **Gross Monthly Income** | **Max Housing (28%)** | **Assumed Other Debt** | **Estimated Max Home Price** | | $50,000 | $4,167 | $1,167 | $250 | ~$165,000 | | $75,000 | $6,250 | $1,750 | $400 | ~$255,000 | | $100,000 | $8,333 | $2,333 | $500 | ~$345,000 | | $150,000 | $12,500 | $3,500 | $700 | ~$525,000 | *Estimates based on 6.75% rate, 30-year term, 10% down, 1.1% property tax, $1,800/yr insurance, 0.5% PMI. Your actual affordability will vary based on your specific debts, credit score, and local costs.* ## Key Factors That Affect How Much Mortgage You Can Afford ### What Lenders Evaluate Lenders use a standardized set of criteria to determine how much they're willing to lend you: - **DTI ratio** — Both front-end and back-end ratios, as described above. This is the primary affordability gatekeeper. Most conventional lenders cap the back-end ratio at [43% per CFPB qualified mortgage standards](https://www.consumerfinance.gov/ask-cfpb/what-is-a-debt-to-income-ratio-why-is-the-43-702702702-702702702-702702702-limit-important-en-1791/). - **Credit score** — Higher scores unlock lower interest rates, which directly increase how much home you can afford on the same monthly payment. A score above 740 typically qualifies for the best conventional rates, per [Freddie Mac's credit score guidance](https://www.freddiemac.com/article/how-your-credit-score-affects-your-mortgage-rate). - **Loan-to-value (LTV) ratio** — The percentage of the home's value you're borrowing. A lower LTV (bigger down payment) reduces lender risk and can improve your terms. - **Employment and income history** — Lenders typically want two years of stable, verifiable income. Self-employed borrowers usually need two years of tax returns. - **Assets and reserves** — Cash reserves after closing (typically 2–6 months of mortgage payments) show lenders you can weather a financial surprise. If you're new to the process, our [real estate terms glossary](https://www.opendoor.com/articles/real-estate-terms-you-should-know) explains these and dozens of other terms you'll encounter. ### What You Should Also Consider Lenders answer "Will we lend you this much?" — but only you can answer "Can I comfortably afford this much?" Consider these factors that don't appear on a loan application: - **Lifestyle costs and personal spending priorities** — Lenders don't know you love to travel, or that you're saving for a child's education. Build your mortgage payment around the life you want, not just the loan you qualify for. - **Future financial goals** — Planning to start a business, go back to school, or retire early? Factor those future income changes into today's decision. - **Emergency fund** — Financial experts generally recommend 3–6 months of living expenses in reserve. If buying a home drains that fund, you may be overextending. - **Home maintenance and repairs** — Budget roughly **1%–2% of your home's value per year** for maintenance. On a $350,000 home, that's $3,500–$7,000 annually. Check out [home improvements that increase value](https://www.opendoor.com/articles/improvements-that-increase-home-value) to learn which repairs are worth prioritizing. - **HOA fees** — These can range from $100 to $700+ per month and are not optional. They're factored into your front-end ratio by lenders, but buyers often underestimate them. ## Common Mistakes When Calculating Mortgage Affordability Even savvy buyers make errors that throw off their affordability estimates. Avoid these pitfalls: ### Forgetting Property Taxes and Homeowners Insurance Your mortgage payment isn't just principal and interest. Property taxes and homeowners insurance are **escrowed into your monthly payment** in most cases and can add $300–$800+ per month depending on your location and home value. According to the [Tax Foundation](https://taxfoundation.org/data/all/state/property-taxes-by-state-county-2024/), effective property tax rates range from 0.31% in Hawaii to 2.23% in New Jersey. Always calculate affordability using the full PITI payment. ### Ignoring Private Mortgage Insurance (PMI) If your down payment is less than 20%, most lenders require PMI, which typically costs **0.3%–1.5% of the original loan amount per year**, according to the [Urban Institute](https://www.urban.org/urban-wire/five-things-know-about-private-mortgage-insurance). On a $300,000 loan, that's $75–$375 per month. It's not permanent — you can request removal once you reach 20% equity — but it significantly affects early-year affordability. ### Overlooking Closing Costs Closing costs for buyers generally run **2%–5% of the purchase price**, according to [Freddie Mac](https://www.freddiemac.com/blog/homeownership/20180927-closing-costs-explained). On a $350,000 home, that's $7,000–$17,500 due at or before closing. These costs don't affect your monthly payment, but they reduce the cash available for your down payment if you haven't budgeted separately. Learn more about [how much it costs to buy a house](https://www.opendoor.com/articles/how-much-does-it-cost-to-buy-a-house) so there are no surprises. ### Using Pre-Approval as Your Budget Ceiling A pre-approval letter tells you the **maximum** a lender will offer — not what you should spend. Lenders don't account for your grocery bill, childcare costs, or retirement contributions. Many financial advisors recommend targeting a payment **10%–15% below** your pre-approved maximum to maintain financial flexibility. ### Not Accounting for Rate Changes Before Closing If you're shopping without a rate lock, interest rates can shift between pre-approval and closing. Even a 0.25% increase changes your monthly payment and total interest paid significantly. Understand [how long closing takes](https://www.opendoor.com/articles/how-long-does-closing-take) and consider locking your rate early if you're in a rising-rate environment. ## What to Do Once You Know Your Budget Calculating your mortgage affordability is the foundation — but it's just the beginning. Here's how to put your number to work: 1. **Get pre-approved** — A pre-approval letter based on your verified financials strengthens your offers. Sellers take pre-approved buyers more seriously, especially in competitive markets. 2. **Search strategically** — Set your home search filters **5%–10% below** your maximum to leave room for bidding and unexpected costs. Understanding [how to make an offer on a house](https://www.opendoor.com/articles/how-to-determine-what-to-offer-on-a-house) helps you negotiate effectively within your budget. 3. **Factor in the full timeline** — From the start of your search to moving day, the process typically takes several months. Our guide on [how long it takes to buy a house](https://www.opendoor.com/articles/briefs/how-long-does-it-take-to-buy-a-house) breaks down each stage. 4. **Schedule inspections** — Before you commit, a thorough inspection can reveal issues that affect a home's true cost. Use our [home inspection checklist for buyers](https://www.opendoor.com/articles/home-inspection-checklist-for-buyers) to know exactly what to look for. 5. **Explore your options on Opendoor** — Once you know what you can afford, browse homes in your budget on Opendoor. You can tour on your schedule, make offers online, and move with confidence. [Get your offer](#) ## Frequently Asked Questions ### How much mortgage can I afford on a $100K salary? Using the 28/36 rule with a 30-year loan at approximately 6.75%, a $100,000 salary supports a maximum housing payment of about **$2,333 per month**. With 10% down and moderate existing debt, that translates to an estimated home price of roughly **$345,000**. Your exact number depends on your debts, credit score, down payment, and local tax rates. ### What is the 28/36 rule for mortgages? The 28/36 rule is a mortgage affordability guideline used by lenders and financial advisors. It says your **monthly housing costs should not exceed 28%** of your gross monthly income (front-end ratio), and your **total monthly debt payments should not exceed 36%** (back-end ratio). It remains the most widely cited rule of thumb for calculating how much house you can afford. ### How do lenders calculate mortgage affordability? Lenders primarily evaluate your **debt-to-income (DTI) ratio**, **credit score**, **loan-to-value (LTV) ratio**, **employment history**, and **cash reserves**. The DTI ratio — both front-end and back-end — carries the most weight. Most conventional lenders prefer a back-end DTI at or below 43%, though government-backed loans sometimes allow higher ratios. ### What DTI ratio do I need to get a mortgage? For conventional loans, most lenders prefer a back-end DTI of **36% or lower**, though many approve borrowers up to **43%**. FHA loans may allow back-end DTI ratios up to **50%** with compensating factors like strong cash reserves or a high credit score. The lower your DTI, the more favorable your loan terms will be. ### Should I use gross or net income for mortgage affordability? Lenders use **gross income** (pre-tax) to calculate your DTI ratios and determine loan eligibility. However, when setting your personal comfort level, many financial advisors recommend thinking in terms of **net (take-home) income** to get a more realistic picture of what you can actually afford after taxes, retirement contributions, and other paycheck deductions. ### How much house can I afford with a $2,000 monthly payment? At a 6.75% interest rate on a 30-year fixed loan, a $2,000 monthly payment (principal and interest only) supports a loan amount of approximately **$308,000**. However, your actual total housing payment also includes property taxes, insurance, and possibly PMI, so the portion available for principal and interest will be less than $2,000. A realistic home price estimate at this payment level is roughly **$290,000–$320,000** depending on local taxes and insurance costs. ### Does mortgage affordability include property taxes and insurance? **Yes.** When lenders calculate your front-end DTI ratio, they use your full **PITI payment** — principal, interest, property taxes, and homeowners insurance. PMI and HOA dues are also included. This is why a home advertised with a "$1,800/month mortgage" may actually cost $2,300–$2,500/month once all components are factored in. ### What's the difference between the front-end ratio and back-end ratio? The **front-end ratio** measures only your housing costs as a percentage of gross income (target: 28% or less). The **back-end ratio** measures your **total debt obligations** — housing plus all other monthly debts — as a percentage of gross income (target: 36% or less). Both ratios are components of the 28/36 rule and are evaluated together by most lenders. ### Can I afford a house if I have student loan debt? Yes, but student loans directly affect your back-end DTI ratio. Even loans in deferment or income-driven repayment may be calculated at **0.5%–1% of the total balance** as a monthly obligation by lenders. Paying down student debt before applying for a mortgage — or choosing an income-driven repayment plan with lower monthly payments — can meaningfully increase the mortgage amount you qualify for. ### Is it better to put 20% down or keep cash in reserves? There's no one-size-fits-all answer. A **20% down payment** eliminates PMI, lowers your monthly payment, and gives you immediate equity. But depleting your savings can leave you vulnerable to unexpected expenses — especially in early homeownership, when [home repairs and renovations](https://www.opendoor.com/articles/eight-ways-to-finance-your-home-renovation-project) are common. Many financial advisors recommend putting down at least 10%–15% while maintaining 3–6 months of expenses in an emergency fund. --- *Originally published at [https://www.opendoor.com/articles/calculate-your-mortgage-affordability](https://www.opendoor.com/articles/calculate-your-mortgage-affordability)*