Interest-Only Payment Calculator

An interest-only loan payment calculator is a financial tool that calculates the payments on an interest-only loan - a loan where the borrower pays only the interest for a specified period (the IO period) before transitioning to fully amortizing payments that include both principal and interest. The interest-only payment calculator computes the initial IO payment, the much higher fully amortizing payment after the IO period ends, the payment shock amount, and the total interest cost during each phase. Our calculator runs entirely in your browser with no data uploaded to any server.

1. Enter Your Loan Details: Input the total loan amount, the annual percentage rate (APR), the interest-only period in years and months, and the total loan term in years. Select your payment frequency - monthly, bi-weekly, or weekly - to match your actual loan structure.
2. Click "Calculate Payments": The interest-only calculator processes your inputs using standard amortization formulas. It calculates the IO payment (interest only) and the fully amortizing payment that applies after the IO period expires. The payment shock - the dollar and percentage increase - is shown prominently with a visual comparison bar chart.
3. Review the Complete Analysis: The calculator displays the interest-only payment amount, the fully amortizing payment after IO, the payment shock at reset, a visual comparison of IO vs amortizing payments, total interest during the IO period, total interest during full amortization, and the combined total interest over the full loan term.

• Interest-Only Payment: The amount you pay each period during the interest-only phase. This covers only the interest accrued on the loan balance; no principal is reduced. The payment is calculated as the loan amount multiplied by the periodic interest rate.
• Fully Amortizing Payment After IO: The new payment amount after the IO period ends, calculated using the standard amortization formula. This payment covers both principal and interest, fully paying off the loan over the remaining term. It is typically 30-60% higher than the IO payment.
• Payment Shock: The dollar and percentage increase between the IO payment and the fully amortizing payment. This is shown with a visual bar chart comparison to make the impact immediately clear. The payment shock represents the additional monthly/budget burden at the reset date.
• Interest Cost Comparison: The total interest paid during the IO period compared to the total interest that will be paid during the amortization period. A combined total shows the full interest cost over the entire loan term.

The interest-only loan payment calculator is 100% free with no signup required. All calculations are performed locally in your browser - your loan amounts, interest rates, and payment details never leave your device. There are no usage limits or caps. The tool supports monthly, bi-weekly, and weekly payment frequencies to match your loan. Use it as many times as you need to model different IO periods, compare loan structures, or plan for the payment reset date.