Auto Loan Refinance Calculator
This calculator compares your existing auto loan to a proposed refinance and supports bi‑weekly and other payment frequencies. It estimates periodic payments, total interest cost, break‑even time and net savings after fees.
Results are estimates intended to help decision making. The model uses standard amortization mathematics and assumes a fixed APR, fixed payment schedule, and fees as entered. Real lender offers may include different terms, rounding rules, or prepayment penalties.
Governance
Record 21516c8ba4f9 • Reviewed by Fidamen Standards Committee
Estimates periodic payments and total interest for the current loan and a proposed refinance. Supports different payment frequencies (monthly, bi‑weekly, weekly) and allows financing of fees or paying them up front.
Inputs
Results
Current periodic payment
-PER 2.08
Total interest remaining (current loan)
-$15,075.00
Refinance periodic payment
-PER 0.30
Total interest (refinance)
-$15,023.08
Estimated interest saved
-$51.92
Estimated net savings after fees
-$51.92
Break‑even (years)
0
| Output | Value | Unit |
|---|---|---|
| Current periodic payment | -PER 2.08 | PER |
| Total interest remaining (current loan) | -$15,075.00 | — |
| Refinance periodic payment | -PER 0.30 | PER |
| Total interest (refinance) | -$15,023.08 | — |
| Estimated interest saved | -$51.92 | — |
| Estimated net savings after fees | -$51.92 | — |
| Break‑even (years) | 0 | years |
Visualization
Methodology
Periodic payment is computed using the standard amortization formula: payment = r * P / (1 - (1 + r)^-n), where r is the periodic interest rate and n is the number of payments.
To compare schedules we convert APR to a periodic rate based on the selected payment frequency (12 = monthly, 26 = bi‑weekly, 52 = weekly) and compute total interest as (payment * number_of_payments) - principal. Financing of fees increases principal accordingly.
Design and quality considerations reference industry standards for numerical methods and software quality. Security and data handling recommendations follow NIST guidance and general ISO quality principles; consult a lender for exact contractual numbers.
Key takeaways
This tool provides an estimated comparison between your current loan and a proposed refinance using standard amortization math and configurable payment frequencies.
Results are planning estimates. Verify final figures with lenders and review official disclosures before refinancing.
Worked examples
Example: $15,000 remaining at 6.0% APR, 3 years left, monthly payments vs refinance to 4.0% APR with bi‑weekly payments and $300 financed fees. The tool will show the new periodic payment, estimated interest saved, and years to recover fees.
Example: Paying a small extra amount each period reduces total interest and can shorten the break‑even time when refinancing fees are present.
F.A.Q.
Does switching to bi‑weekly always save money?
Not always. Bi‑weekly schedules can reduce interest by increasing effective payment frequency, but actual savings depend on APR, whether fees are financed, payment rounding rules, and whether your lender applies payments immediately to principal. Use the calculator inputs to model your precise scenario and verify with your lender.
Are these numbers exact for legal disclosure?
No. These are estimates for planning purposes only. Lender disclosures (including APR, payment rounding, timing, and fees) determine legally binding amounts. For loan closing figures, rely on the lender's Good Faith Estimate or final disclosure.
How accurate are the calculations and what are the limits?
Calculations use standard amortization formulas and double‑precision arithmetic assumptions. They do not model variable interest rates, prepayment penalties, escrow, or irregular extra payments beyond the single extra payment field. Rounding and lender-specific application of payments may change results. See the accuracy caveats and standards references below.
How is my data handled?
This tool performs calculations locally in your browser; do not enter sensitive personal data beyond loan numeric fields. For production deployment, follow NIST SP 800‑63 (digital identity) and NIST cybersecurity guidance for handling, transmitting, and storing financial data.
Sources & citations
- NIST (National Institute of Standards and Technology) — https://www.nist.gov
- ISO (International Organization for Standardization) — https://www.iso.org
- IEEE (Institute of Electrical and Electronics Engineers) — https://www.ieee.org
- OSHA (Workplace safety standards reference) — https://www.osha.gov
- Consumer Financial Protection Bureau — Loan and mortgage information — https://www.consumerfinance.gov
- CFPB Regulation Z — 12 CFR § 1026.22 Determination of Annual Percentage Rate — https://www.consumerfinance.gov/rules-policy/regulations/1026/22/
- CFPB Appendix J — Annual Percentage Rate Computations for Closed-End Credit — https://www.consumerfinance.gov/rules-policy/regulations/1026/j/
- CFPB Annual Percentage Rate Tables — https://www.consumerfinance.gov/compliance/compliance-resources/other-applicable-requirements/annual-percentage-rate-tables/
Further resources
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: 21516c8ba4f9What changed (latest)
v1.0.0 • 2025-11-19 • 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
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-19 • 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 19, 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 • 2025-11-19 • 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: dbc9a04b7624
- https://www.consumerfinance.gov
- https://www.consumerfinance.gov/compliance/compliance-resources/other-applicable-requirements/annual-percentage-rate-tables/
- https://www.consumerfinance.gov/rules-policy/regulations/1026/22/
- https://www.consumerfinance.gov/rules-policy/regulations/1026/j/
- https://www.ieee.org
- https://www.iso.org
- https://www.nist.gov
- https://www.osha.gov