Fidamen

Auto Loan Payment Calculator

This calculator estimates periodic payments, financed amount, total paid, and total interest for a fixed-rate auto loan. It accounts for down payment, trade-in value, fees, and sales tax applied to the taxable vehicle amount.

Use it to compare monthly, biweekly, or other payment schedules by adjusting payments per year. Results are planning estimates and may differ from lender disclosures due to rounding or fee treatment.

Updated Nov 18, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record b3710b9f35a2 • Reviewed by Fidamen Standards Committee

Inputs

Results

Updates as you type

Financed amount

$29,660.00

Periodic payment

$559.72

Total of all payments

$33,583.25

Total interest paid

$3,923.25

OutputValueUnit
Financed amount$29,660.00USD
Periodic payment$559.72USD
Total of all payments$33,583.25USD
Total interest paid$3,923.25USD
Primary result$29,660.00

Visualization

Methodology

We apply the standard amortizing loan formula with periodic rate r = APR / 100 / payments_per_year and total payments n = term_years × payments_per_year.

Financed amount equals taxable base plus fees and sales tax. Taxes are modeled as a percentage of the taxable base (price minus down payment and trade-in).

Results are rounded for display. Lenders may use different day-count or compounding conventions.

Worked examples

Example: $30,000 price, $3,000 down, $0 trade-in, 8% tax, $500 fees, 5% APR, 5 years, monthly payments → financed amount ≈ $28,540; payment ≈ $539. (Illustrative.)

F.A.Q.

How is sales tax applied?

This model applies sales tax to the taxable base (price minus down payment and trade-in). Local rules vary; confirm with your dealer or tax authority.

Are results guaranteed to match lender quotes?

No. This is an estimate for planning. Lenders may apply different rounding or fee conventions.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: b3710b9f35a2

What changed (latest)

v1.0.0 • 2025-11-18 • 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 18, 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 • 2025-11-18 • 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: 8dbd175ade6a