What This Calculator Does
The Income Needed to Buy a House Calculator estimates the gross annual salary you would need to qualify for a specific mortgage. Lenders cap your monthly housing costs at a percentage of your gross income — known as the front-end debt-to-income (DTI) ratio, commonly 28%. This tool works backward from the home's total monthly payment to reveal the income required to stay within that limit. Dollar amounts assume US-style conventions, but the math applies to any currency.
How to Use It
Enter the loan amount (the mortgage, not the full home price), the interest rate, and the loan term in years. Add your estimated annual property tax and home insurance so the full housing payment (PITI) is captured. Finally, set the maximum percentage of income a lender allows for housing — 28% is the standard front-end ratio. The calculator returns the annual and monthly income you'd need, along with the monthly payment breakdown.
The Formula Explained
First we compute the monthly principal and interest using the amortization formula, where i is the monthly rate and n is the number of payments. We add monthly property tax and insurance to get the total monthly housing payment. Then required annual income = (monthly payment ÷ DTI ratio) × 12. A lower DTI ratio means more income is required for the same payment.
$$\text{Income} = \frac{\left(M + \frac{\text{Tax}}{12} + \frac{\text{Insurance}}{12}\right) \times 12}{\text{DTI}/100}$$ $$\text{where}\quad \left\{ \begin{aligned} M &= \text{Loan} \cdot \frac{r\,(1+r)^{n}}{(1+r)^{n}-1} \\ r &= \dfrac{\text{Rate}}{1200} \\ n &= \text{Term} \times 12 \end{aligned} \right.$$
Worked Example
For a $300,000 loan at 6.5% over 30 years, the principal & interest is about $1,896.20/month. Adding $300 tax and $100 insurance gives a $2,296.20 monthly payment. At a 28% DTI ratio, required annual income = $$\left(\frac{2{,}296.20}{0.28}\right) \times 12 \approx \$98{,}409 \text{ per year.}$$
FAQ
What DTI ratio should I use? 28% is the conventional front-end limit; some loan programs allow higher. Lower ratios give a more conservative, comfortable estimate.
Does this include my other debts? No — this is the front-end (housing-only) ratio. Car loans and credit cards affect the separate back-end ratio (often 36–43%).
Should I use the loan or the home price? Enter the loan amount after your down payment. A larger down payment lowers the loan and the income required.
