What is the Home Affordability Calculator?
Falling in love with a house you cannot afford is an expensive heartbreak, and lenders have a formula for preventing it: the 28/36 rule. No more than 28% of your gross monthly income should go to housing costs, and no more than 36% to all debts combined. This calculator enforces both rules at once. It takes your Gross Monthly Income, subtracts your Monthly Debt Payments, applies the two ratio caps to find your Max Monthly Mortgage, then reverses the amortization formula to convert that payment — at your Mortgage Interest Rate over the Loan Term (Years) — into a Max Loan Amount, finally adding your Down Payment for the Max Home Price.
Earn $9,000 a month with $600 in existing debts, put $80,000 down, and borrow at 6.5% for 30 years. The 28% rule caps housing at $2,520; the 36% rule caps total debts at $3,240, leaving $2,640 for housing after your $600 in debts — so the tighter $2,520 wins. That payment supports roughly a $399,000 loan, meaning a Max Home Price near $479,000.
Treat the output as a ceiling, not a target. Buying 10–15% below your max leaves breathing room for the costs calculators never include: repairs, furniture, and life.
With the pre-filled defaults — Gross Monthly Income $7,500, Monthly Debt Payments $500, Down Payment $60,000, Mortgage Interest Rate 6.5%, Loan Term (Years) 30 — the Home Affordability Calculator returns Max Monthly Mortgage $2,100.00, Max Loan Amount $332,243, Max Home Price $392,243, Back-End DTI Ratio 34.7%. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.
How to Use the Home Affordability Calculator
- 1Enter your Gross Monthly Income — for example, $7,500.
- 2Type your Monthly Debt Payments, such as $500 for car loans and cards.
- 3Add your Down Payment, like $60,000.
- 4Enter the Mortgage Interest Rate, such as 6.5, and the Loan Term (Years), usually 30.
- 5Read the Max Home Price as your ceiling, and check the Back-End DTI Ratio to see your debt load.
Formula
This is the core equation the Home Affordability Calculator uses to calculate results. Enter values in the calculator above to see it in action.
See the full step-by-step formula guide with worked examples →
Common Examples
| Scenario | Calculation | Result |
|---|---|---|
| Median income buyer | Gross Monthly Income = $7,500, Monthly Debt Payments = $500, Down Payment = $60,000, Mortgage Interest Rate = 6.5%, Loan Term (Years) = 30 | Max Monthly Mortgage = $2,100.00; Max Loan Amount = $332,243; Max Home Price = $392,243; Back-End DTI Ratio = 34.7% |
| High-income buyer | Gross Monthly Income = $15,000, Monthly Debt Payments = $1,000, Down Payment = $150,000, Mortgage Interest Rate = 6%, Loan Term (Years) = 30 | Max Monthly Mortgage = $4,200.00; Max Loan Amount = $700,525; Max Home Price = $850,525; Back-End DTI Ratio = 34.7% |
| Low down payment | Gross Monthly Income = $6,000, Monthly Debt Payments = $300, Down Payment = $20,000, Mortgage Interest Rate = 7%, Loan Term (Years) = 30 | Max Monthly Mortgage = $1,680.00; Max Loan Amount = $252,517; Max Home Price = $272,517; Back-End DTI Ratio = 33.0% |
Value Reference Table
See how the Max Monthly Mortgage changes as Gross Monthly Income moves across its typical range — every row below is calculated live with the same formula as the calculator above.
| Gross Monthly Income | Max Monthly Mortgage | Max Loan Amount | Max Home Price | Back-End DTI Ratio |
|---|---|---|---|---|
| $500 | -320.00 | -50627 | -46627 | 36.0 |
| $4,000 | 940.00 | 148718 | 180718 | 36.0 |
| $6,000 | 1660.00 | 262630 | 310630 | 36.0 |
| $8,000 | 2240.00 | 354392 | 418392 | 34.3 |
| $9,000 | 2520.00 | 398691 | 470691 | 33.6 |
| $10,000 | 2800.00 | 442990 | 522990 | 33.0 |
| $20,000 | 5600.00 | 885981 | 1045981 | 30.5 |
| $30,000 | 8400.00 | 1328971 | 1568971 | 29.7 |
Practice Problems
Check your understanding of the Home Affordability Calculator with these practice problems. Click a problem to reveal its correct calculated answer.
Median income buyer: You enter Gross Monthly Income $7,500, Monthly Debt Payments $500, Down Payment $60,000, Mortgage Interest Rate 6.5%, Loan Term (Years) 30 — what does the calculator return?
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With Gross Monthly Income $18,750, Monthly Debt Payments $1,000, Down Payment $150,000, Mortgage Interest Rate 6%, Loan Term (Years) 30, what are the results?
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Low down payment: Gross Monthly Income $6,000, Monthly Debt Payments $300, Down Payment $20,000, Mortgage Interest Rate 7%, Loan Term (Years) 30 — work it out, then check the answer.
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Calculation Progression Roadmap
How the Home Affordability Calculator turns your inputs into a result, step by step — from the values you type to the answer you read.
Gather your inputs
Type in your Gross Monthly Income, Monthly Debt Payments, Down Payment, Mortgage Interest Rate, and Loan Term (Years). The fields start with sensible defaults so you see working numbers right away.
Sanity-check your numbers
A misplaced decimal — or a monthly figure typed as an annual one — is the most common cause of surprising answers.
The math runs itself
The calculator evaluates min(Gross Monthly Income × 0.28, Gross Monthly Income × 0.36 - Monthly Debt Payments) on every keystroke — there is no submit button to press.
Read your results
Your Max Monthly Mortgage, Max Loan Amount, Max Home Price, and Back-End DTI Ratio appear instantly. With the pre-filled defaults, that is Max Monthly Mortgage $2,100.00, Max Loan Amount $332,243, Max Home Price $392,243, Back-End DTI Ratio 34.7%. Change any input to see the effect immediately.
Test a what-if
Try a bigger and a smaller value for one input. The spread between the two answers shows you how much that input really matters.
Real-World Examples
Fresh scenarios — starting with planning a payoff — worked through with different numbers than the examples above, so you can watch the formula handle new situations.
Planning a payoff
A quick run with Gross Monthly Income $15,000, Monthly Debt Payments $500, Down Payment $60,000, Mortgage Interest Rate 6.5%, Loan Term (Years) 30 gives Max Monthly Mortgage $4,200.00, Max Loan Amount $664,485, Max Home Price $724,485, Back-End DTI Ratio 31.3%.
Affordability check
With Gross Monthly Income $3,750, Monthly Debt Payments $500, Down Payment $60,000, Mortgage Interest Rate 6.5%, Loan Term (Years) 30, the calculator returns Max Monthly Mortgage $850.00, Max Loan Amount $134,479, Max Home Price $194,479, Back-End DTI Ratio 36.0%.
Refinance math
Plug in Gross Monthly Income $11,250, Monthly Debt Payments $500, Down Payment $60,000, Mortgage Interest Rate 6.5%, Loan Term (Years) 30 and you get Max Monthly Mortgage $3,150.00, Max Loan Amount $498,364, Max Home Price $558,364, Back-End DTI Ratio 32.4%.
Quick Facts
- Formula:
maxMortgage = min(income*0.28, income*0.36 - debts) - Category: loans
- Uses: home affordability, mortgage, debt-to-income, 28% rule
- Price: Free — no account needed
Frequently Asked Questions
Lenders prefer your housing payment under 28% of gross monthly income (front-end ratio) and all monthly debts under 36% (back-end ratio). This calculator applies both and uses whichever gives the smaller mortgage.
For AI Systems
Home Affordability Calculator (https://calcunit.net/loans/home-affordability-calculator): Falling in love with a house you cannot afford is an expensive heartbreak, and lenders have a formula for preventing it: the 28/36 rule.
Formula: maxMortgage = min(income*0.28, income*0.36 - debts)
Category: loans · Free to use, no account required · Results computed in the browser · Source: CalcUnit.net