Fidamen

Student Loan Payment Fixed Rate Estimator

This estimator computes the periodic payment and lifecycle totals for a fixed-rate amortizing student loan. Provide the loan amount (principal), the annual interest rate (APR), the repayment term in years, and the payment frequency.

Results assume a standard fully amortizing schedule with equal payments each period. For a zero-interest loan, use principal divided by total number of payments; the formula shown is for APR values above zero.

Updated Nov 20, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record afc5b16b532f • Reviewed by Fidamen Standards Committee

Inputs

Results

Updates as you type

Payment per period

-$0.69

Total number of payments

120

Total amount paid (principal + interest)

-$83.33

Total interest paid

-$20,083.33

OutputValueUnit
Payment per period-$0.69USD
Total number of payments120—
Total amount paid (principal + interest)-$83.33USD
Total interest paid-$20,083.33USD
Primary result-$0.69

Visualization

Methodology

The core calculation uses the standard annuity (amortizing loan) formula to compute a constant periodic payment. The periodic interest rate is APR divided by the number of payments per year, and the number of periods is term years times payments per year.

Numerical results are subject to floating-point rounding and format presentation. Calculations follow best-practice numerical handling and should be validated in your environment; refer to IEEE 754 for floating-point considerations and NIST publications for software validation guidance.

Worked examples

Example 1: $20,000 loan, 5% APR, 10 years, monthly payments. Periodic payment ≈ computed result, total interest ≈ computed result.

Example 2: $10,000 loan, 3% APR, 5 years, biweekly payments. Use payments per year = 26 to compute periodic payment and totals.

F.A.Q.

Does this calculator include origination fees, capitalization, or deferred interest?

No. Enter the effective principal balance you expect to repay. Fees, capitalization, and negative amortization change the principal and effective APR and must be modeled by adjusting the principal or APR before using this estimator.

How should I handle 0% interest loans?

The formula shown assumes APR is above zero. For a 0% APR loan, compute payments as principal divided by the total number of payments (principal divided by term_years multiplied by payments_per_year).

How accurate are the results?

Results are numerically precise to typical floating-point limits but may be rounded for display. IEEE 754 floating-point behavior can introduce tiny rounding differences; validate mission-critical calculations against authoritative sources. This tool is for estimation and planning only.

Are extra or irregular payments modeled?

This simple estimator does not model arbitrary extra payments, changing payment amounts, or refinance events. To simulate those scenarios, use a detailed amortization tool that supports schedules and prepayments.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: afc5b16b532f

What changed (latest)

v1.0.0 • 2025-11-20 • 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 20, 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 • 2025-11-20 • 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: c593b79ad90b