Fidamen

Business Loan APR Calculator with Extra Payments

This calculator estimates the scheduled payment, payoff timing, total paid, and interest paid for a business loan and shows how recurring extra payments and/or a one-time lump-sum payment change those outcomes. It is intended for planning and comparison, not as a legally binding APR disclosure.

Results assume a fixed-rate, fully amortizing loan with payments at a constant frequency. When you apply extra payments the tool recomputes the effective payoff schedule and estimates cumulative interest savings relative to the scheduled amortization.

Updated Nov 5, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 978f30bfe264 • Reviewed by Fidamen Standards Committee

Apply a recurring extra payment starting after an optional delay and a one-time lump-sum at a specified payment. Estimates payoff timing and savings.

Inputs

Results

Updates as you type

Balance after lump-sum

$49,301.61

Estimated remaining payments after lump-sum

59

Estimated total interest

$9,403.60

Interest saved vs scheduled

$0.00

OutputValueUnit
Balance after lump-sum$49,301.61USD
Estimated remaining payments after lump-sum59periods
Estimated total interest$9,403.60USD
Interest saved vs scheduled$0.00USD
Primary result$49,301.61

Visualization

Methodology

The tool computes a periodic interest rate by dividing the annual APR by the number of payments per year. For scheduled payments it uses the standard annuity formula to compute the periodic payment that amortizes the loan over the stated term.

When recurring extra payments are applied, the calculator treats the extra amount as added to each periodic payment and computes the number of periods until the balance reaches zero using closed-form algebraic formulas for an amortizing loan (logarithmic solution). For a lump-sum paydown, the balance immediately post-payment is computed and remaining periods are re-derived using the annuity relations.

This estimate models interest accrual by period and assumes payments are applied at the scheduled interval with extras applied as specified. It does not simulate arrears, fees, deferred interest, variable rates, payment holidays, or lender-specific application order rules.

Key takeaways

Use the baseline method to see scheduled amortization. Use recurring, lump-sum, or combined methods to compare how extra payments reduce payoff time and interest.

This tool provides planning estimates. For lender-provided payoff quotes, contact your loan servicer to get exact balances and payoff instructions.

F.A.Q.

Is this calculator producing the legally required APR used for consumer disclosures?

No. This tool estimates amortization and effective payoff impacts from extra payments. Legal APR disclosures (Truth in Lending Act / similar) may require inclusion of fees and specific rounding and must follow regulatory methods used by lenders and regulators.

How accurate are the payoff estimates when I add extra payments?

Estimates use closed-form amortization formulas and assume payments and extras are applied exactly as entered. Minor differences can occur due to rounding, lender-specific interest accrual conventions, payment application order, and timing adjustments.

What inputs should I check to ensure reasonable results?

Confirm the APR, payment frequency, term length, and whether your lender compounds interest at the same frequency. Ensure recurring extra amounts and lump sums reflect how and when you will actually pay them.

Are there limits on inputs?

This tool assumes positive principal and non-negative APR. Extremely small payments that do not cover per-period interest may produce very long or effectively indefinite payoff estimates; the tool flags such cases by returning large payoff values.

Sources & citations

Further resources

External guidance

Versioning & Change Control

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

Record ID: 978f30bfe264

What changed (latest)

v1.0.0 • 2025-11-05 • 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 5, 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 • 2025-11-05 • 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: bfd927c35637