Income to Mortgage Calculator
Calculate how much house you can afford based on your income.
Uses the 28/36 rule to estimate your maximum mortgage and home price.
The income-to-mortgage ratio determines the maximum mortgage you qualify for based on your gross income, debts, and prevailing interest rates. Lenders use debt-to-income (DTI) ratios as the primary qualifying tool.
The Key Ratios:
Front-end DTI (housing ratio) = Monthly housing payment / Gross monthly income ≤ 28%
Back-end DTI (total debt ratio) = (Housing + All monthly debts) / Gross monthly income ≤ 36–43%
Maximum Mortgage Formula:
Max monthly payment = Gross monthly income × 0.28
Max mortgage = Max monthly payment × Loan factor
Loan factor at 7% APR, 30-year term ≈ 150 (meaning $1 of monthly payment supports ~$150 of loan)
Worked Example:
Annual income: $90,000 → Gross monthly: $7,500
Max housing payment: $7,500 × 28% = $2,100/month
Max mortgage (7% APR, 30yr): $2,100 × 150 = $315,000
With existing debts (car $400/month, student loan $200/month): Back-end DTI: ($2,100 + $600) / $7,500 = 36% — just within conventional lending limits.
Down Payment Impact:
If home price is $375,000 with 20% down ($75,000): mortgage = $300,000 — fits within the $315,000 limit.
Interest Rate Sensitivity:
| Mortgage Rate | Monthly Payment on $300,000 | Income Needed (28% DTI) |
|---|---|---|
| 5% | $1,610 | $69,000/year |
| 6% | $1,799 | $77,000/year |
| 7% | $1,996 | $85,500/year |
| 8% | $2,202 | $94,000/year |
Practical Tips:
- Lenders use gross income, not net — before taxes
- Rental income counts at 75% of gross rent for qualifying
- FHA loans allow back-end DTI up to 50% in some cases; conventional loans typically cap at 43%
- A larger down payment reduces the mortgage and monthly payment without requiring more income
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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