Fidamen

Home Loan Refinance Calculator with Extra Payments

This calculator helps you decide whether to refinance your home loan or continue with your existing mortgage while applying optional extra monthly or one-time payments. It reports monthly payments, total interest and fees, break-even months, and estimated payoff time when adding extra payments.

Values are estimates intended for planning and comparison only. Use the inputs to model realistic refinance fees, proposed rates, and any extra payments you may make. Results assume fixed-rate, level-payment amortization and monthly compounding unless you specify otherwise.

Updated Nov 21, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record efc00086d55e • Reviewed by Fidamen Standards Committee

Compares total cost, interest, monthly payments and break-even for refinancing while accounting for extra payments and upfront refinance fees.

Inputs

Results

Updates as you type

Current monthly payment (effective)

$1,389.58

New monthly payment (base)

$1,088.02

Net monthly savings

$301.57

Break-even (months)

10

Estimated net interest savings

$22,188.67

Total interest & fees on new loan

$144,685.69

Remaining interest on current loan

$166,874.36

Months to pay off current loan with extras

300

Total interest if you keep loan and add extras

$166,874.36

OutputValueUnit
Current monthly payment (effective)$1,389.58USD
New monthly payment (base)$1,088.02USD
Net monthly savings$301.57USD
Break-even (months)10months
Estimated net interest savings$22,188.67USD
Total interest & fees on new loan$144,685.69USD
Remaining interest on current loan$166,874.36USD
Months to pay off current loan with extras300months
Total interest if you keep loan and add extras$166,874.36USD
Primary result$1,389.58

Visualization

Methodology

Calculations use standard amortization formulas to compute level monthly payments and remaining interest for fixed-rate mortgages. When an explicit current monthly payment is not provided, the tool derives it from the remaining balance, remaining term, and current rate.

Refinance comparison includes upfront refinance fees and both recurring and one-time extra payments. Break-even months are computed as refinance fees divided by net monthly savings. Payoff time with extra payments uses the closed-form solution for amortizing a loan with a fixed payment and monthly compounding.

Key takeaways

Use conservative inputs for fees and realistic extra payments when comparing scenarios.

This tool is for planning; consult your lender for exact payoffs, escrow changes, or loan-specific terms before acting.

F.A.Q.

Does this calculator include taxes, insurance, or escrow?

No. This tool models principal and interest and allows extra payments and refinance fees. Add taxes or escrow components separately to the monthly payment inputs if you want them included in comparisons.

Are results exact?

Results are estimates based on mathematical amortization formulas. Actual payments and interest will vary with loan-specific rounding, escrow changes, or lender adjustments. See accuracy caveats in citations.

What if my current loan has prepayment penalties?

Prepayment penalties are not modelled automatically. Enter any known penalty as an additional one-time fee (e.g., in refinance fees or extra_one_time_payment) to accurately reflect costs.

How should I use the break-even result?

Break-even months estimate how long it takes for monthly savings to offset upfront refinance fees. Use it alongside your expected time in the home and total interest savings to decide whether to refinance.

Sources & citations

Further resources

External guidance

Versioning & Change Control

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

Record ID: efc00086d55e

What changed (latest)

v1.0.0 • 2025-11-21 • 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 21, 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 • 2025-11-21 • 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: 3415448ed343