Fidamen

Student Loan Adjustable Rate Calculator

This calculator estimates payments for adjustable-rate student loans. It supports two principal modes: amortizing loans and interest-only initial periods. You can enter a full annual rate or compute the rate as index + margin.

Use the form to simulate an example rate adjustment at the next reset. Results include the initial periodic payment, outstanding balance at the first reset, and an example post-adjustment payment. These are illustrative estimates, not a repayment schedule.

Updated Nov 19, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 9b50400ef53d • Reviewed by Fidamen Standards Committee

Standard amortizing loan that uses an initial rate for a fixed period then adjusts according to index/margin and caps. Calculates initial payment, outstanding balance at first reset, and example re-set payment.

Inputs

Advanced inputs

Index / Margin inputs

Results

Updates as you type

Initial periodic payment

-$0.69

Outstanding balance at first reset

$27,533.00

Example payment after adjustment

-$2.10

Example payment change

20286.30%

OutputValueUnit
Initial periodic payment-$0.69USD
Outstanding balance at first reset$27,533.00USD
Example payment after adjustment-$2.10USD
Example payment change20286.30%%
Primary result-$0.69

Visualization

Methodology

The tool computes periodic rates from annual percentage rates and payment frequency, then applies standard amortization formulas to derive periodic payments and remaining balances.

When an initial fixed or interest-only period ends, this calculator models an example single adjustment using an expected change to the annual rate (percentage points). It applies standard formulas to compute the outstanding principal at reset and then the amortizing payment required over the remaining term.

Caps and lifetime limits are surfaced as inputs and shown in the glossary; users should verify contract terms and how caps are actually applied by their lender. This calculator does not enforce contractual cap calculations beyond providing fields to capture them for user awareness.

F.A.Q.

Is this an exact repayment schedule?

No. This tool produces illustrative example payments and balances using standard formulas. Actual schedules depend on exact contract terms, rounding rules, amortization conventions, and how your servicer applies caps and index resets.

Does the calculator enforce contractual caps and margin rules?

The calculator exposes cap fields for awareness but does not automatically apply complex legal cap-roll rules beyond the simple illustrative example. Always consult your loan contract or servicer to confirm cap behavior.

What inputs should I use for the index?

Enter the current published index value your loan references (for example a published short-term rate) and the lender margin. If uncertain, use the rate shown on your loan statement or contact the servicer.

How accurate are the results?

Results use standard actuarial formulas. Accuracy depends on input correctness and assumptions about index changes, rounding, and payment timing. See the accuracy caveats and standards references below.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: 9b50400ef53d

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: 73fa5a577c9b