Fidamen

Personal Loan Refinance Calculator with Extra Payments

This tool helps you compare your existing personal loan to a refinance offer and estimate how recurring extra payments or a one-time lump sum accelerate payoff and reduce total interest. It models monthly payment formulas and provides straightforward break-even and savings estimates.

Use the inputs to represent your remaining principal, current APR and remaining months, and a proposed refinance APR/term/fees. Add recurring extra payments or an upfront lump sum to see the impact on months-to-payoff and interest.

Updated Nov 12, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 42f12a0d54e7 • Reviewed by Fidamen Standards Committee

Compare current loan vs new refinance offer, compute monthly payments, interest paid, and months to break even on fees.

Inputs

Results

Updates as you type

Current monthly payment

$480.49

New monthly payment (refinance)

$371.17

Monthly savings

$109.33

Total interest savings (estimate)

-$18.21

Estimated months to break even

5

OutputValueUnit
Current monthly payment$480.49USD
New monthly payment (refinance)$371.17USD
Monthly savings$109.33USD
Total interest savings (estimate)-$18.21USD
Estimated months to break even5months
Primary result$480.49

Visualization

Methodology

Monthly payments are computed using the standard amortization formula: payment = P * r / (1 - (1+r)^-n), where r is the monthly interest rate (annual rate / 12) and n is total months. Refinance calculations add upfront fees to the new principal before computing the new payment.

For extra monthly payments, the tool estimates the shortened payoff by solving for the number of payments required when the payment is increased by the extra monthly amount. A one-time lump sum applied immediately reduces principal before amortization. Results are numerical estimates; see accuracy caveats below.

Key takeaways

Use refinance comparison to determine if lower APR and terms offset upfront fees.

Use extra payments modeling to see how recurring extras or a lump sum reduce months to payoff and total interest.

All outputs are estimates; verify with lender statements for exact figures and consider prepayment penalties and fee timing.

F.A.Q.

Should I include refinance fees in the new principal?

Yes. This tool adds upfront refinance fees to the refinance principal to produce an apples-to-apples comparison of total cost and monthly payment. If fees are paid separately out of pocket, enter 0 and manually account for them in your decision.

Can I model a lump sum applied later instead of now?

This version models an immediate lump-sum application (apply now). If you plan to apply a lump sum later, treat the early payoff estimate as optimistic. For precise later-date modeling, compute the remaining principal at that future date and re-run the tool with that principal as the starting balance.

Are the results exact?

Results are mathematical estimates based on standard amortization formulas and assume fixed rates and monthly compounding. They do not account for daily interest accrual conventions, payment date differences, fees charged at different times, prepayment penalties, or taxes. See citations and accuracy caveats.

What if monthly savings are zero or negative?

If the refinance does not reduce the monthly payment (monthly savings is zero or negative), break-even in months is not meaningful. The calculator will show a large or undefined break-even period. Always review assumptions and consult loan documents.

Sources & citations

Further resources

External guidance

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 42f12a0d54e7

What changed (latest)

v1.0.0 • 2025-11-12 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

UI

v1.0.0

Governance

Last updated: Nov 12, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

  • MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
  • MINOR: New features or fields that do not change existing outputs for the same inputs.
  • PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

  • Verify formulas and unit definitions against primary standards or datasets.
  • Run golden-case regression suite and edge-case suite.
  • Record reviewer sign-off with credentials and scope.
  • Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

  • Uses exact unit definitions from the Fidamen conversion library.
  • Internal calculations use double precision; display rounding follows the unit's configured decimal places.
  • Not a substitute for calibrated instruments in regulated contexts.
  • Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-12 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: e857469722e6