Interest-Only Mortgage Calculator
Compare interest-only vs fully amortized payment structures to manage short-term cash flow.
Input your parameters to generate the Interest-Only Mortgage Calculator results.
How to Use This Calculator
Get accurate results in seconds by following these simple steps.
Enter Loan Details
Input the principal balance, interest rate, and the length of the interest-only period.
Set Full Amortization Term
Enter the total loan term to see what happens when conversion to P&I begins.
Compare Both Payments
View the low IO payment against the dramatically higher fully-amortized payment side by side.
Why Use This Tool?
Cash Flow Flexibility
Interest-only periods let investors maximize cash flow during the initial property build-up phase.
Payment Shock Warning
See exactly how much your payment jumps when the IO period expires and principal amortization begins.
Strategy Validation
Confirm whether an IO loan makes sense for your investment timeline or if full amortization is safer.
How Interest-Only Mortgages Function
Interest-Only mortgages offer the lowest possible initial monthly payment by completely deferring principal repayment. During the introductory 'IO Period' (typically 5 to 10 years), you are strictly paying the monthly interest generated by the loan balance.
The danger of these loans lies in the 'Recast'. Once the IO period ends, the entire original loan balance must now be fully amortized and paid off over a severely shortened timeline.
For example, if you have a 30-year loan with a 10-year IO period, you must ultimately pay off the entire 30-year balance in only 20 years. This causes massive 'Payment Shock', and this calculator shows exactly how severe that shock will be.
Frequently Asked Questions
They are popular with real estate investors aiming to maximize monthly cash flow, house flippers who intend to sell the asset quickly, or extremely high-net-worth borrowers with massive variable incomes.
No. Unless the housing market appreciates, your loan balance will remain identical on day 3,650 as it was on day 1. You only begin paying down debt after the recast.
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