Certified Financial Planner (CFP) with 15 years of experience in debt management and retirement planning.
Find out how a one-time lump sum payment can shorten your loan and save you in interest. Enter your current loan details and your extra payment amount to see the impact.
Early Loan Repayment (Lump Sum) Calculator
Loan Amortization Formulas
This calculator compares two scenarios: your original loan and a new loan with a reduced principal (Original Balance – Lump Sum). It uses these two formulas to find the total interest paid in both cases.
2. n = -log(1 – (P*r)/M) / log(1+r)
- M: Monthly Payment
- P: Principal Loan Amount
- r: Monthly Interest Rate (Annual Rate / 12)
- n: Total Number of Payments
- log: Natural Logarithm
Related Calculators
- Extra Payment Calculator (Monthly)
- Amortization Schedule Calculator
- Loan Balance Calculator
- Bi-Weekly Payment Calculator
What is an Early Loan Repayment?
An early loan repayment, or lump sum payment, is when you pay a large, one-time amount toward your loan’s principal, in addition to your regular monthly payments. Unlike an extra monthly payment, this is often done after receiving a bonus, inheritance, or tax refund.
The benefit is twofold: First, this payment is applied directly to the principal, immediately reducing the amount of money you owe. Second, because your balance is lower, the amount of interest you are charged in all future months is also lower, leading to significant savings and a shorter loan term.
How to Calculate Lump Sum Savings (Example)
You have a $250,000 loan at 6.5% with 25 years remaining. Your monthly payment is $1,677.10. You make a one-time $20,000 lump sum payment.
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Step 1: Calculate Original Total Interest:
Total Payments (Original) = $1,677.10 * 300 (25 yrs * 12) = $503,130
Total Interest (Original) = $503,130 – $250,000 = $253,130 -
Step 2: Calculate New Loan Term:
New Principal (P) = $250,000 – $20,000 = $230,000
We find the new term (n) using the ‘n’ formula with the *original* monthly payment ($1,677.10).
n = -log(1 – (230000 * (0.065/12)) / 1677.10) / log(1 + (0.065/12))
New Term (n) ≈ 251.5 months (a savings of 48.5 months) -
Step 3: Calculate New Total Interest:
Total Payments (New) = ($1,677.10 * 251) + (Final Payment) ≈ $421,000
Total Interest (New) = $421,000 – $230,000 = $191,000 -
Step 4: Find Total Savings:
Interest Saved = $253,130 – $191,000 = $62,130
Time Saved = 300 – 251.5 = 48.5 Months (or 4 years)
Frequently Asked Questions (FAQ)
This depends on your loan’s interest rate vs. the potential after-tax return you could get from investing. If your loan rate is high (e.g., 7%), paying it off is a guaranteed 7% “return”. If your rate is low (e.g., 3%), you might earn more by investing in the market over the long term, though this comes with risk.
Sometimes. This is called a “prepayment penalty”. It’s common in some (but not all) mortgages, auto loans, and business loans. You MUST check your loan agreement or ask your lender before making a large lump sum payment.
When you make the payment, you must explicitly instruct your lender to “apply to principal”. If you don’t, they might just apply it as an “advance payment” for future months, which does not save you nearly as much interest.