Repayment Calculator
Project the exact payoff date and total interest cost at any monthly payment level and see how increasing the payment reshapes both the timeline and the total cost.
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Enter your values above to see the results.
Tips & Notes
- ✓Even $50 extra per month applied consistently to principal shortens most 4-5 year loans by 3-6 months and saves several hundred dollars in interest.
- ✓Bi-weekly payments instead of monthly result in 26 half-payments annually — equivalent to one extra full payment per year with no significant change to cash flow.
- ✓Always confirm with your servicer that extra payments are applied to principal, not to advance future scheduled payments, which provides no interest benefit.
- ✓The highest-rate loan in your portfolio should receive any extra payment — targeting the highest rate first minimizes total interest across all debts.
- ✓Rounding up your monthly payment to the nearest $50 or $100 is a low-friction way to accelerate payoff without committing to a formal extra payment schedule.
- ✓Review your loan payoff timeline after any income increase — directing even half of a raise toward loan payoff dramatically compresses the repayment schedule.
Common Mistakes
- ✗Making extra payments without confirming they reduce principal — servicers sometimes apply additional funds to prepay future scheduled payments rather than reducing the balance.
- ✗Focusing on minimum payments to maximize cash flow without modeling total interest cost — minimum payment behavior on an 8% loan is an expensive long-term choice.
- ✗Not prioritizing high-rate debt first when making extra payments across multiple loans — random extra payments eliminate less total interest than targeted payoff strategy.
- ✗Ignoring the opportunity to refinance high-rate debt before aggressively paying it down — a 3% rate reduction on $20,000 saves $3,000+ that no extra payment strategy can replicate.
- ✗Treating loan payoff as all-or-nothing — making inconsistent extra payments still saves meaningful interest even when you cannot maintain a fixed elevated payment.
- ✗Forgetting that paying off any loan early requires a formal payoff quote from the servicer — the scheduled balance differs from the true payoff amount due to daily interest accrual.
Repayment Calculator Overview
A repayment calculator answers a different question than a standard loan calculator — instead of starting from a loan amount to find a payment, it starts from a payment amount to show when the debt ends and what it costs. This is particularly useful when you already have a loan and want to model what happens if you pay more or less each month.
Understanding the relationship between payment amount, payoff time, and total interest gives you control over the outcome rather than just accepting the lender default.
What each field means:
- Loan Amount — the current outstanding balance you are repaying
- Interest Rate — annual rate on the existing loan; determines how fast interest accrues each month
- Loan Term — the original or remaining repayment period used to calculate the standard payment
- Down Payment — not applicable for repayment modeling; enter 0 for existing balances
What your results mean:
- Monthly Payment — the required fixed payment to pay off the balance in the stated term
- Total Paid — all payments over the full term at this payment level
- Total Interest — what the lender earns at the standard payment level
- Interest-to-Principal — proportion of every payment going to interest versus reducing balance
Example — $18,000 balance at 8.5% remaining, 4-year payoff:
Standard monthly payment: $447 Total paid over 48 months: $21,456 Total interest: $3,456 With $100 extra/month ($547 total): New payoff: 38 months (10 months early) Interest saved: $692 With $200 extra/month ($647 total): New payoff: 31 months (17 months early) Interest saved: $1,089
EX: Same $18,000 at 8.5% — different payment scenarios $350/month: 63 months to payoff, total interest $4,050 $447/month (standard): 48 months, total interest $3,456 $600/month: 33 months, total interest $2,356 $900/month: 21 months, total interest $1,474 Doubling the payment cuts the repayment period by more than half.
Months to payoff by payment amount — $20,000 at 8.0%:
| Monthly Payment | Months to Payoff | Total Interest |
|---|---|---|
| $300 | 90 months | $7,000 |
| $400 | 60 months | $4,000 |
| $500 | 45 months | $2,500 |
| $700 | 31 months | $1,700 |
Extra payment impact — $20,000 at 8.0% / 5-year standard term:
| Extra Monthly | Months Saved | Interest Saved |
|---|---|---|
| $0 | 0 | $0 |
| $50 | 5 months | $540 |
| $100 | 9 months | $960 |
| $200 | 16 months | $1,680 |
Paying more than the minimum on any loan is one of the highest guaranteed-return financial moves available. On an 8% loan, every extra dollar you pay earns a guaranteed 8% return by eliminating future interest — risk-free. This often compares favorably to savings accounts and bonds, making accelerated debt repayment a meaningful part of any personal finance strategy.
Frequently Asked Questions
The exact formula is complex, but the calculator handles it instantly. Mathematically, the number of payments n = -log(1 - r x P / M) / log(1 + r), where P is the balance, r is the monthly rate (annual rate divided by 12), and M is the monthly payment. For a $20,000 balance at 8% with a $500/month payment: n = -log(1 - 0.00667 x 20,000 / 500) / log(1.00667) = approximately 45 months. The key insight: increasing the payment even slightly shortens the term disproportionately because less principal carries forward each month.
The minimum viable payment is anything above the monthly interest that accrues. For a $20,000 balance at 8%, monthly interest is approximately $133. A payment of $134 would technically make progress, but it would take decades. The standard minimum payment lenders set is calculated to pay off the balance in the original loan term. Any payment below that minimum actually extends the loan beyond the original term. The calculator shows you exactly what different payment levels produce in terms of payoff time and total interest.
The savings compound non-linearly. On a $20,000 balance at 8% over 5 years, the standard payment is $405/month and total interest is $4,300. Adding $100 extra ($505/month) saves approximately $960 in interest and cuts 9 months off the term. Adding $200 extra saves $1,680 and cuts 16 months. The savings per extra dollar are highest in the early payments when the balance is largest and interest accrual is greatest. This is why starting extra payments immediately produces more benefit than the same payments made after a few years.
If the loan rate exceeds the after-tax return you can reliably earn on savings, paying off the loan is the better choice — it is a guaranteed return equal to the interest rate. For a loan at 8%, the savings would need to earn more than 8% consistently to justify holding the debt. In practice, savings accounts earn 4-5% and investments are uncertain. The exception is building an emergency fund first — depleting cash reserves to pay off debt creates vulnerability that can force high-cost borrowing later. Keep 3-6 months of expenses liquid, then direct surplus to loan payoff.
Paying off a loan early does not hurt your credit score in any lasting way. Closing an installment account reduces the number of open accounts and can slightly lower your average account age, which may cause a temporary minor dip. However, the positive effect of lowering your overall debt and completing a loan in good standing outweighs this. The account remains on your credit report as a positive closed account for 10 years, continuing to benefit your payment history score. Any temporary dip from early payoff is typically less than 10 points and recovers within a few months.
The current balance shown on your statement is the balance as of the statement date. Because interest accrues daily on most loans, by the time you make a payment, the actual amount needed to fully satisfy the loan is slightly higher than the last statement balance. The payoff amount is calculated as of a specific future date and includes all accrued interest through that day. Always request a formal payoff quote from your servicer with a specific payoff date before sending a final payment — sending the statement balance will leave a small remaining balance that continues accruing interest.