Mortgage & financing
Interest-only Mortgage Payment Calculator
Show interest-only payments, unchanged principal and the payment increase when the loan starts amortizing.
Calculate your result
What this calculator estimates
Calculate an interest-only payment and compare it with amortizing debt. It combines the inputs below to produce Monthly interest-only payment. Every assumption remains editable so the estimate can reflect the property, financing and location being evaluated.
Worked example
Using the displayed sample assumptions, the calculator produces $2,000. This is an illustration, not a market quote. Change one input at a time to understand what drives the result.
Inputs and assumptions
- Loan amount — sample input: 400000 currency units
- Annual interest rate — sample input: 6 %
- Interest-only period — sample input: 5 years
- Total loan term including interest-only period — sample input: 25 years
- Upfront loan fees — optional — sample input: 0 currency units
How to interpret the result
Compare the payment with your total housing budget, not income alone. Compare a conservative case with an expected case and keep a record of the assumptions used.
Common mistake to avoid
Avoid assuming the lowest advertised rate applies to every borrower. Local definitions, taxes, lending practices and measurement requirements can materially change the result.
Calculation details
Interest-only interest uses annual rate ÷ 12. The subsequent amortizing loan uses the selected market convention. No principal is paid during the interest-only period.
Results included
- Monthly interest-only payment
- Annual interest-only payments
- Interest during interest-only period
- Balance at end of interest-only period
- Monthly payment after interest-only period
- Monthly payment increase
- Principal due as balloon
- Total interest and fees
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Reviewed 2026-09-08.