Fidamen

Personal Loan Amortization Calculator

This amortization engine models personal loan repayment under multiple schedules: standard bi‑weekly (26 equal payments per year), accelerated bi‑weekly (half of the monthly payment applied every two weeks), and a monthly baseline for comparison. Enter principal, APR, term, and any constant extra payment to see periodic payment, total paid, total interest and estimated payoff time.

Results are calculated from standard amortization formulas. The calculator provides estimates for planning and comparison; actual lender schedules, rounding rules, payment application order, and fees can change outcomes.

Updated Nov 17, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 64f42ef7bb10 • Reviewed by Fidamen Standards Committee

Calculates a fixed periodic payment using 26 payments per year. Supports an optional constant extra payment applied to each bi‑weekly installment.

Inputs

Results

Updates as you type

Bi‑weekly payment

-$0.33

Total paid over life of loan

-$43.27

Total interest paid

-$15,043.27

Payoff time (years)

5

Number of payments

130

OutputValueUnit
Bi‑weekly payment-$0.33USD
Total paid over life of loan-$43.27USD
Total interest paid-$15,043.27USD
Payoff time (years)5years
Number of payments130payments
Primary result-$0.33

Visualization

Methodology

We use discrete periodic compounding consistent with the selected payment frequency. The primary formulas derive the periodic interest rate as APR/periods-per-year and solve the annuity payment equation to compute required payment or number of periods.

For accelerated bi‑weekly, we compute the monthly payment first (12 periods/year), then set the bi‑weekly payment equal to half that monthly payment and solve for the number of bi‑weekly periods required to amortize the principal at the bi‑weekly periodic rate. This reflects the common accelerated bi‑weekly practice of creating an extra monthly payment over the year.

Worked examples

Example: $15,000 loan, 7.5% APR, 5 years — standard bi‑weekly payment is computed with 26 periods/year. Accelerated bi‑weekly equals half the monthly payment and typically reduces payoff time and interest by creating the effect of one extra monthly payment per year.

Add a constant extra payment per bi‑weekly installment to see direct reductions in payoff time and interest across all methods.

F.A.Q.

What is the difference between standard and accelerated bi‑weekly?

Standard bi‑weekly uses 26 equal payments derived from the bi‑weekly annuity formula. Accelerated bi‑weekly sets the payment equal to half the monthly payment; because 26 half‑monthly payments equal 13 full monthly payments, this accelerates repayment and reduces interest.

Does this tool include fees or prepayment penalties?

No. This calculator does not include origination fees, late fees, prepayment penalties, or irregular payments. Enter additional fees as part of the loan principal or adjust results to account for penalties separately.

How accurate are the payoff estimates?

Estimates use standard mathematical models for amortization. Actual amortization may differ due to lender rounding rules, payment application order (principal vs interest), payment dates, and any account fees. See accuracy and standards citations below.

Can I model one‑time extra payments or varying extra payments?

This version supports a constant extra payment applied to each periodic installment. For one‑time or irregular extra payments, use an exportable amortization schedule and apply the extra payment at the appropriate date in a custom schedule tool.

Sources & citations

Further resources

External guidance

Versioning & Change Control

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

Record ID: 64f42ef7bb10

What changed (latest)

v1.0.0 • 2025-11-17 • 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 17, 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 • 2025-11-17 • 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: fd04fda57683