Example data table
| Example inputs | Value | Example outputs | Value |
|---|---|---|---|
| Original amount | 250,000 | Current payment | 1,580.17 |
| APR / term | 6.50% / 30y | Estimated current balance | 241,043.10 |
| Payments made | 36 | Reamortized payment | 1,416.28 |
| Lump sum / fee | 25,000 / 300 | Interest saved vs current | 28,099.95 |
Formula used
- Payment: PMT = r·PV / (1 − (1+r)−n), where r is rate per period, PV principal, n periods.
- Balance after k payments: Bk = PV(1+r)k − PMT·((1+r)k − 1)/r.
- Reamortized balance: B’ = max(0, B − lumpSum) + feeRolledIn.
- Schedule: each period uses Interest = Balance·r, Principal = Payment − Interest, and updates the balance.
How to use this calculator
- Enter the original loan amount, APR, term, and payment frequency.
- Choose how to set the balance: payments made or exact balance.
- Add your planned lump-sum principal payment (if any).
- Select a reamortization mode: recast, new term, or keep payment.
- Click Calculate to see results above the form.
- Download the schedule as CSV or a PDF summary report.
Payment impact after reamortization
Reamortization recalculates payments using the remaining balance and term. In the example above, a $250,000 loan at 6.50% with 30 years and monthly payments has a $1,580.17 payment. After 36 payments, the estimated balance is $241,043.10. Applying a $25,000 lump sum and recasting over 324 remaining payments lowers the required payment to $1,416.28. If you switch to biweekly payments (26/year), the same logic applies, but the per‑period rate and period count change, which can shift payoff dates and totals.
Interest cost trade-offs
Lower payments usually mean more interest over time. Keeping the current plan on the remaining balance produces about $270,931.99 of future interest. The recast schedule reduces that to about $242,832.04, saving roughly $28,099.95, while still ending on the original payoff date. If you keep the old payment after the lump sum, payoff can shorten to about 250 payments, with future interest near $178,641.24.
Setting a new remaining term
Selecting “New term” lets you target a specific horizon. Periods equal remainingYears × paymentsPerYear, so 15 years at monthly payments is 180 periods. Compared with 324 periods, that is 144 fewer payments, a 44% reduction. The payment rises because principal must be repaid faster, but total interest generally falls when the rate is unchanged.
Fees and break-even checks
Many lenders charge a reamortization fee; the example uses $300. Paying it upfront affects cash flow only once. Rolling it into the balance increases principal by $300, adding about $1.63 of first‑month interest at 6.50%/12. With a payment drop of $163.89 ($1,580.17 − $1,416.28), the upfront fee is recovered in about 2 months of lower payments.
Using exports to verify totals
The schedule export lists payment, principal, interest, and ending balance each period. Confirm that interest equals prior balance × periodic rate and that principal equals payment minus interest. Totals should satisfy: totalPaid = totalPrincipal + totalInterest. Use CSV to audit every line, and PDF to share a summary during lender discussions. Compare lender statements to exported totals.
FAQs
1) What is loan reamortization?
It recalculates your required payment using today’s remaining balance, interest rate, and remaining term. The payoff date usually stays similar unless you choose a new term or keep the old payment.
2) When should I use “Recast” versus “Keep payment”?
Choose recast to lower the required payment while keeping roughly the same remaining horizon. Choose keep payment to shorten the payoff timeline after a lump sum, typically increasing interest savings but not lowering the payment.
3) Does a lump-sum payment always save interest?
Usually yes, because it reduces principal immediately. The amount saved depends on the rate, remaining term, and whether you also lower the payment. Keeping the same payment after the lump sum tends to maximize interest savings.
4) Can I model a new rate without refinancing?
You can enter a new rate to see “what-if” outcomes, but changing the contractual rate usually requires a refinance or lender modification. Use the new-rate option to compare scenarios, not as a guarantee of approval.
5) Why choose “payments made” or “enter balance”?
If you know your exact balance, entering it is most accurate. If not, the calculator estimates balance from the original terms and payments made. Small differences can occur due to lender rounding, escrow, or fee timing.
6) How do CSV and PDF exports help?
CSV lets you audit every line: payment, principal, interest, and balance. PDF provides a compact summary for sharing. Use them to validate totals, compare options side-by-side, and discuss details with your lender or advisor.