How is Prepayment Interest Calculated?
Understand the exact daily reducing balance mathematics behind loan prepayments and simulate how reducing principal saves thousands in compound interest.
Explore specialized calculators, mathematical formula guides, and accelerated repayment strategies:
📐 The Fundamental Prepayment Mathematics
In an amortizing loan (such as home mortgages, auto loans, or personal loans), interest is not a fixed flat fee. It is calculated dynamically based on the current outstanding balance.
Where P = current principal, r = annual interest rate as a decimal.
Immediate drop in P lowers all future interest accrued every single day thereafter.
Interactive Interest Simulator
Prepayment Injection Details
📊 Exact Step-by-Step Calculation:
- Scheduled Monthly EMI: $0
- Principal Reduction: Prepaying $0 lowers balance in Month 12.
- New Loan Term: Payoff accelerated by 0 months.
Amortization Schedule
Interactive breakdown of balance, interest, and prepayment impact
| Period | EMI Paid | Principal Paid | Extra Prepayment | Interest Paid | Total Payment | Remaining Balance |
|---|
Frequently Asked Questions
How is prepayment interest calculated on loans?
Most banks calculate interest on a Daily Reducing Balance basis. The daily interest formula is: Daily Interest = (Outstanding Principal × Annual Interest Rate) ÷ 365. When you make a prepayment, the outstanding principal immediately drops. From that exact day forward, subsequent interest is calculated on the lower principal, permanently shrinking future interest charges.
Does prepayment go towards interest or principal first?
When an EMI is paid, it first covers the accrued monthly interest, with the remaining portion reducing principal. However, when you make a dedicated part-prepayment, 100% of that extra amount goes directly to reducing the principal balance.
What is the formula to calculate interest saved from prepayment?
Total Interest Saved = Total Scheduled Interest (Original) - Total Revised Interest (After Prepayments). Because amortizing loans front-load interest, early prepayments generate an exponential compounding return.
Is interest calculated monthly or daily on mortgages?
In modern retail banking (including India, US, UK, Australia, and Canada), interest is accrued daily based on the day's closing principal balance and debited/compounded monthly at the end of each billing cycle.