Interest Only Mortgage Calculator
Use this calculator to generate an amortization schedule for an interest only mortgage.
How the interest only mortgage calculator works
During the interest-only period you pay just the monthly interest, so the balance never shrinks. The calculator shows that low payment, then the higher payment once the full balance must amortize over the shorter remaining term.
Worked example: with loan amount of $400,000, interest rate of 6.50% and total term (years) of 30, the interest-only mortgage calculator shows interest-only payment of $2,166.67.
- Interest-only payment
- $2,166.67
- Payment after IO period
- $2,982.29
- Standard P&I payment
- $2,528.27
- Interest paid during IO
- $260,000
The formula
Interest-only payment = balance × monthly rate. After the IO period the payment becomes P × r ÷ (1 − (1 + r)⁻ⁿ) over the remaining months.
Results are estimates for educational purposes and are not financial advice. Confirm exact figures with your lender, plan administrator or advisor.
Questions about the interest only mortgage calculator
What happens when the interest-only period ends?
Your payment jumps, sometimes sharply, because the entire balance now has to be repaid over fewer remaining years. The calculator shows the size of that jump.
Who should consider an interest-only mortgage?
Borrowers with irregular or rising income who want low initial payments and a plan to refinance, sell, or pay down principal voluntarily before the reset.
Do I build any equity during the interest-only period?
Not through payments — your balance stays flat. Equity only grows if the property appreciates or you make voluntary principal payments.
Is the Interest Only Mortgage Calculator free to use?
Yes. Every calculator on FinCalculators is completely free, with no sign-up, login or paywall. You can run as many scenarios as you like.