Interest-Only Mortgage Calculator
See your interest-only payment now, and your fully-amortizing payment after the IO period ends.
Enter your numbers and select Calculate to see results.
About This Calculator
Interest-only mortgages let you pay only the interest for an initial period (often 5–10 years), keeping payments lower at first. This calculator shows your interest-only payment, and — critically — the much larger fully-amortizing payment you'll owe once that period ends and you begin paying down principal over the remaining term.
How This Is Calculated
IO Payment = Loan Amount × (Annual Rate ÷ 12)
- IO Payment
- — Interest-only monthly payment
- Fully-Amortizing Payment
- — Standard payment once principal repayment begins, calculated over the remaining term
A $400,000 loan at 6.75% has an interest-only payment of $2,250/month. After a 10-year IO period on a 30-year loan, the remaining 20 years requires about $3,043/month — a 35% jump.
Assumptions
- Assumes a fixed rate throughout; many interest-only loans are adjustable-rate, which would change these figures.
- No principal is paid during the interest-only period.
Frequently Asked Questions
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Last updated January 15, 2026. Results are estimates for informational purposes only — read our disclaimer.