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Interest-Only Mortgage Calculator

Free interest-only mortgage calculator. Compare the interest-only payment to the full principal & interest payment.

See the low interest-only payment now and the larger principal & interest payment that begins once the interest-only period ends.

How the Interest-Only Mortgage Calculator works

During the interest-only period you pay only the monthly interest, so the balance doesn't fall. The calculator also shows the higher principal-and-interest payment that begins afterward.

Example calculation

On a $400,000 loan at 6.75%, interest-only is about $2,250 a month, while the later P&I payment jumps to roughly $2,594 once amortization begins.

Tips for using the Interest-Only Mortgage Calculator

  • You build no equity during the interest-only phase.
  • Plan for the payment jump before it hits.
  • Best for disciplined borrowers with irregular income.

Interest-Only Mortgage Calculator — frequently asked questions

Do I build equity?
Not during the interest-only period — the balance does not go down unless you make extra payments.
Who is it for?
Borrowers with irregular income who understand the payment will rise sharply later.
Why choose interest-only?
Lower initial payments for cash-flow flexibility, used cautiously by some investors and high earners.
Can I pay principal voluntarily?
Yes — extra principal during the IO period reduces the future payment jump.

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