Fidamen

Personal Loan Adjustable Rate Calculator

This calculator projects payments for an adjustable-rate personal loan by modeling periodic rate resets based on an index plus a margin, subject to user-specified periodic caps, lifetime caps, and a rate floor.

Use conservative assumptions about index movement and caps. Results are estimates for planning and educational use only; they do not substitute for product disclosures or licensed financial advice.

Updated Nov 2, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record caffa9180ba9 • Reviewed by Fidamen Standards Committee

Projects payments for an amortizing personal loan that re-sets periodically based on an index plus margin, subject to periodic and lifetime caps and a rate floor. Produces initial payment, payment after the first adjustment, and payment if the rate reaches the lifetime cap.

Inputs

Results

Updates as you type

Initial payment

$193.33

Annual rate after first adjustment (%)

650.00%

Payment after first adjustment

$195.22

Remaining principal at first adjustment

$8,231.97

Payment at lifetime cap (immediate)

$217.42

OutputValueUnit
Initial payment$193.33USD
Annual rate after first adjustment (%)650.00%%
Payment after first adjustment$195.22USD
Remaining principal at first adjustment$8,231.97USD
Payment at lifetime cap (immediate)$217.42USD
Primary result$193.33

Visualization

Methodology

We assume an amortizing loan with fixed periodic payments that are recalculated at each scheduled rate reset. The interest rate at each reset equals the then-current index plus the specified margin, then is limited by the periodic cap and lifetime cap and not allowed below the rate floor.

The calculator derives an implied current index from the initial APR and margin, projects index movement according to your annual assumption, applies caps per adjustment, computes remaining principal at a reset using closed-form amortization formulas, and then recomputes the payment for the remaining term.

F.A.Q.

What is being assumed about the index?

The calculator infers the current index by subtracting the margin from the initial APR. Future index movement is a user-supplied annual percentage change projected to each adjustment period; this is a simplified straight-line assumption for scenario analysis.

Are caps and floors applied?

Yes. Periodic caps limit the maximum change at each reset (both up and down in this model). Lifetime cap limits the total increase over the initial APR. The rate floor prevents the rate from dropping below a set annual percentage.

How accurate are these projections?

These are mathematical projections using closed-form amortization formulas. They do not model stochastic index paths, prepayments, fees, or lender-specific rounding rules. Real payments may differ due to day-count conventions, compounding conventions, administrative fees, or changes to loan terms.

Is this legal or financial advice?

No. This tool provides estimates for planning only. Consult the loan contract, product disclosures, and a licensed financial professional before making decisions.

Sources & citations

Further resources

External guidance

Versioning & Change Control

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

Record ID: caffa9180ba9

What changed (latest)

v1.0.0 • 2025-11-02 • 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 2, 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 • 2025-11-02 • 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: ad2c7a76859d