15% Fixed-Rate Mortgage Calculator
Evaluate extreme lending scenarios. Compares the total cost of a 15% loan against renting and investing strategies.
15% Mortgage Payment
Total Loan Cost:
Difference to Invest
If invested at 7% for 30 yrs:
About
A 15% mortgage rate is an outlier in modern finance, typically reserved for distressed assets, speculative development, or hyper-inflationary economies. The compound effect at this rate is severe: the borrower often pays the value of the house in interest alone within the first 7-10 years. This tool is built to visualize that "wealth transfer" from borrower to lender.
The calculator includes a specific comparison for "Renting + Investing." When mortgage rates exceed stock market average returns (historically 7-10%), it is mathematically advantageous to rent a comparable property and invest the difference between the high mortgage payment and the lower rent. This tool helps quantify that opportunity cost.
Formulas
Total Cost C over term n is:
At 15%, the monthly interest factor is 0.0125. The compounding frequency creates a debt curve that remains nearly flat for the first decade.
Reference Data
| Scenario | Total Paid over 30 Years | Multiple of House Price |
|---|---|---|
| 15% Mortgage | $4,550,000 | 4.55x |
| 12% Mortgage | $3,700,000 | 3.70x |
| 7% Mortgage | $2,400,000 | 2.40x |
| Cash Purchase | $1,000,000 | 1.00x |