Interest-Only Mortgage Calculator
Last updated: October 15, 2026
Estimate the initial interest-only payment, later principal-and-interest payment and total interest for an interest-only mortgage.
Initial interest-only payment
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- Later principal-and-interest payment: —
- Payment increase after interest-only period: —
- Estimated total interest: —
- Principal remaining after interest-only period: —
On this page
Quick summary: Estimate the initial interest-only payment, later principal-and-interest payment and total interest for an interest-only mortgage.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate the initial interest-only payment, later principal-and-interest payment and total interest for an interest-only mortgage.
How to use it
Enter Loan amount ($); Annual interest rate (%); Total loan term (years); Interest-only period (years). Select Calculate to update the results.
How the calculation works
During the interest-only period, the monthly payment is the loan balance multiplied by the monthly interest rate. The remaining balance is then amortized over the months left in the original term.
Worked example: starting scenario
| Loan amount ($) | 500000 |
|---|---|
| Annual interest rate (%) | 6.5 |
| Total loan term (years) | 30 |
| Interest-only period (years) | 10 |
| Initial interest-only payment | $2,708.33 |
|---|---|
| Later principal-and-interest payment | $3,727.87 |
| Payment increase after interest-only period | $1,019.53 |
| Estimated total interest | $719,687.76 |
| Principal remaining after interest-only period | $500,000.00 |
Important limitations
Many interest-only loans have adjustable rates, balloon provisions or qualification rules that are not modeled. Taxes, insurance, fees and prepayment terms are excluded.