$300,000 Mortgage: Monthly Payment

Rate Table: $300,000 at Illustrative Rates

At the low end of the table, a 4% rate over 30 years produces a P&I of about $1,432. At the high end, an 8% rate pushes that same loan to approximately $2,201. The 15-year column shows higher monthly payments but dramatically lower total interest — the lifetime cost at 6% over 15 years is roughly $155,000 less than the same rate stretched over 30 years.

Each row makes one thing clear: rate sensitivity is real and it scales with loan size. On $300,000, every quarter-point rate increase adds roughly $50 to $55 per month over 30 years. Over the full term, that quarter-point costs an additional $18,000 to $20,000 in total interest. These figures are computed using the standard amortization formula and are illustrative — your lender's rate sheet determines the actual rate available to you.

What Income Supports a $300,000 Mortgage

Under the 28% front-end DTI guideline used in conventional underwriting, your total housing payment — including taxes and insurance — should not exceed 28% of gross monthly income. If your full PITI on a $300,000 loan at an illustrative 6.5% rate is around $2,400 per month (after adding taxes and insurance to the $1,896 P&I), you would need a gross monthly income of roughly $8,570, or about $103,000 per year, to stay within the 28% line.

The back-end ratio adds car payments, student loans and credit-card minimums into the picture. If those other debts total $400 per month, your combined obligations are $2,800, and the 36% back-end ceiling requires about $7,780 per month gross — roughly $93,000 per year. The lower of the two thresholds is the binding constraint. Use the affordability calculator linked below to run these DTI checks with your own numbers.

All rates shown are illustrative. Income thresholds are based on the 28/36 DTI guideline and will differ if your lender uses other qualification criteria.