The Home Affordability Calculator is a free browser-based tool that answers the first question every buyer asks: how much house can I actually afford on my salary? Instead of starting from a loan amount and working forward to a monthly payment — that is what a mortgage calculator does — this tool starts from your income and existing debts, applies the industry-standard 28/36 debt-to-income (DTI) rule, and runs the result backward through a loan formula to surface the maximum home price in your realistic range. The whole thing runs in any modern browser on macOS, so Mac users get the full experience without downloading an app, creating an account, or trusting a third-party spreadsheet with their numbers. Every input and every result is processed locally in your browser; nothing is uploaded, saved, or shared, which matters when you are typing in your actual salary, debt balances, and savings.
Why a Browser-Based Tool Fits a Mac Workflow
Most Mac users already keep Safari or Chrome pinned to the dock and use the browser for nearly everything. A calculator that lives in a web page slots into that habit instead of fighting it. There is no .dmg to download, no system extension to approve, no Gatekeeper warning to dismiss, and no background process eating RAM after you close the tab. The page is the app: open it, type your numbers, read the answer, close the tab. Because the tool processes everything client-side, you can also use it on a Mac that is locked down by an employer's IT policy, on a shared family iMac, or on a MacBook Air running off an airport lounge Wi-Fi network without worrying about whether a server captured your salary.
For readers who already use the browser as their main finance workspace, the calculator behaves the same way other browser tools do: your inputs stay in the form, every change to a field instantly updates the result, and you can hit refresh to start over without losing your place in a workflow. If you have been searching for a way to estimate home affordability without spinning up Excel, Numbers, or a dedicated macOS finance app, this is the lightest path that still uses the lender-grade 28/36 framework.
How to Run the Home Affordability Calculator on Mac
Working through the calculator takes less than a minute once you have your numbers in front of you. Use this sequence on any Mac running a modern browser.
- Open the calculator page in your browser. Bookmark it if you plan to come back as your income or debts change.
- Enter your gross monthly or annual income. Choose whether the income is monthly or annual so the tool converts it correctly.
- Add your total recurring monthly debt payments. Include car loans, student loans, credit-card minimums, personal loans, and any other fixed obligations that show up on a credit report.
- Enter the cash down payment you plan to bring to closing. Leave it at zero to see the loan-only ceiling; raise it to see how savings expand your reach.
- Type your expected annual interest rate and the loan term in years (15, 20, or 30 are the most common choices).
- Read the three outputs: affordable home price, affordable loan amount, and maximum monthly housing payment. Each is recalculated the instant you change any input above.
If you want a second pass after seeing the first result, change one variable at a time — switch the loan term from 30 to 15 years, bump the rate up or down to reflect current quotes, or trim the down payment to see how much leverage you are giving up. Because every input recalculates instantly, you can run a dozen scenarios in a sitting without leaving the page.
Each Input Field and What to Enter
| Field | What to put in |
|---|---|
| Gross income | Your pay before taxes and deductions. Toggle monthly or annual to match how you think about it. |
| Monthly debts | The sum of every recurring debt payment you already owe each month. |
| Down payment | Cash you will put down at closing, separate from any loan proceeds. |
| Annual interest rate | The rate you expect the lender to quote, expressed as a percent (for example 6.75, not 0.0675). |
| Loan term | How many years you plan to amortize the loan. 30 is standard; 15 cuts interest but raises the monthly bill. |
How the 28/36 Rule Sets Your Ceiling
The 28/36 rule applies two separate caps to your gross monthly income, and is widely used by lenders as part of the standard debt-to-income ratio framework. The front-end ratio says housing costs should not exceed 28% of gross income. The back-end ratio says all recurring debt — your future mortgage plus car loans, student loans, and minimum credit-card payments — should not exceed 36%. Your maximum monthly housing budget is the smaller of the two: min(0.28 × income, 0.36 × income − monthly debts).
Worked example, all on a single income:
- Gross monthly income: $8,000
- Other recurring monthly debts: $600 (car loan $300, student loan $200, credit-card minimums $100)
- Front-end cap: 0.28 × $8,000 = $2,240
- Back-end cap: 0.36 × $8,000 = $2,880; $2,880 − $600 = $2,280
- Maximum housing budget: min($2,240, $2,280) = $2,240 (front-end ratio binds)
In this case the front-end ratio is the tighter constraint, which is the common pattern when existing debts are modest. If the debts were $2,500 instead of $600, the back-end cap would fall to $380 and become the binding ceiling — and if debts ever exceed 36% of income, the back-end calculation goes negative and the housing budget is forced to zero. That zero result is the tool telling you the existing debt load has to come down before a new mortgage makes sense.
That monthly ceiling then feeds into an inverse amortization formula to convert dollars-per-month into a maximum loan amount at your chosen rate and term, and the down payment is added on top to give the affordable home price. The exact loan math involves raising (1 + monthly rate) to the power of the total number of payments, which is why the calculator handles it in the browser rather than expecting you to do it by hand.
Reading the Three Output Numbers
| Output | What it represents |
|---|---|
| Affordable home price | The top of your realistic buying range: maximum loan plus your down payment. |
| Affordable loan amount | The largest mortgage the 28/36 ceiling will support at your chosen rate and term. |
| Maximum monthly housing payment | The principal-and-interest payment you can carry, used as the input for the inverse loan formula. |
Treat the affordable home price as a ceiling, not a target. If your real search tops out well below it, you have headroom for higher property taxes, insurance, or PMI. If the search forces you toward that ceiling, you are at the edge of what the 28/36 framework considers safe.
What the Estimate Leaves Out
The 28/36 ceiling is a lender guideline, not a guarantee of approval. Actual underwriting also weighs your credit score, cash reserves after closing, employment history, and the specific loan program — FHA, VA, and conventional loans each apply their own limits, and some lenders stretch ratios higher for strong files. The calculator covers principal and interest only; your true monthly cost will add property taxes, homeowners insurance, HOA dues, and possibly private mortgage insurance (PMI) when the down payment is under 20%. Those line items reduce the home price you can comfortably carry, so the output is best read as a starting benchmark for your search and for conversations with a licensed mortgage professional.
Scenarios Worth Trying on Your Mac
Because the page recalculates on every keystroke, the most useful thing you can do is run scenarios that answer questions you actually have. Drop the loan term from 30 years to 15 and watch the affordable price fall as the monthly ceiling absorbs a larger payment — that is the cost of paying off the house faster. Drop the interest rate by half a point and see how much reach a small refinance quote could buy you. Raise the down payment by $10,000 increments and watch the affordable price climb, which is a quick way to see whether saving for another year is worth it. Finally, double your monthly debts temporarily to see exactly how much car or student loan balances are costing you in house price — many buyers are surprised at how aggressively high debts shrink the realistic budget. For a deeper walkthrough of the inputs and the formula behind the scenes, the Inside the Home Affordability Calculator Formula guide shows the same calculation broken out step by step.
When you are ready to turn the estimate into a real offer, take the three numbers to a lender for a formal pre-approval. The 28/36 figure tells you what the math says you can carry; the lender will tell you what they are actually willing to underwrite, including the taxes, insurance, and PMI that the browser tool intentionally leaves out.
For a deeper look, see Home Affordability Calculator on Windows in Any Browser.