Reviewed by: David Chen, CFA
David Chen is a Certified Financial Analyst with over 10 years of experience in mortgage analytics and lump-sum repayment strategies.
David Chen is a Certified Financial Analyst with over 10 years of experience in mortgage analytics and lump-sum repayment strategies.
Use this free mortgage calculator one time extra payment to see how a single lump-sum toward principal can slash interest and months off your loan.
Mortgage Calculator One Time Extra Payment
Result will appear here
Not calculated yet.
One-Time Extra Payment Formula
Original Interest: total interest without extra
New Interest: total interest with lump-sum applied
Interest Saved: Original – New
Formula Sources: Investopedia | Bankrate
Variables
- Loan Amount: Original principal balance.
- Rate & Term: Used to compute standard amortization.
- Extra Amount: Lump-sum applied directly to principal.
- Extra Month: Timing of the payment (earlier = bigger savings).
Related Calculators
- Bi-Weekly Extra Payment Calculator
- Mortgage Refinance Break-Even Calculator
- Mortgage Payoff Goal Calculator
- Extra Payment vs Investment Calculator
What Is a One-Time Extra Payment Mortgage Calculator?
It shows the impact of a single lump-sum principal payment—such as a bonus, tax refund, or inheritance—on your mortgage. Applying it early reduces the balance ahead of schedule, shrinking total interest and shortening the loan term.
How to Calculate One-Time Extra Payment (Example)
- Enter your original loan amount, rate, and term.
- Input the lump-sum you plan to pay (e.g., $10,000).
- Specify the month when you’ll make the extra payment (e.g., month 12).
- Click “Calculate” to see months saved and total interest avoided.