Fidamen

Student Loan Fixed Rate Calculator

This calculator estimates the required payment per period, the total amount paid over the loan term, and the total interest paid for a fixed-rate student loan. It uses the standard annuity payment formula and accepts custom payment frequency (for example monthly or annual payments).

Use this tool for planning and comparison. It does not model variable-rate loans, income-driven repayment plans, deferments, or amortization schedule changes caused by extra principal payments; see methodology and caveats for details.

Updated Nov 9, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 1bc38def0f7a • Reviewed by Fidamen Standards Committee

Inputs

Results

Updates as you type

Payment per period

$212.13

Total paid (all periods)

$25,455.72

Total interest paid

$5,455.72

OutputValueUnit
Payment per period$212.13USD
Total paid (all periods)$25,455.72USD
Total interest paid$5,455.72USD
Primary result$212.13

Visualization

Methodology

The calculator applies the annuity (fixed-payment) formula for amortizing loans. Periodic interest rate equals APR divided by the number of payments per year. Number of periods equals term (years) times payments per year.

Numeric behavior and rounding follow best practices for financial calculators: we apply IEEE 754-compatible arithmetic and round displayed currency values to two decimal places. For algorithm validation and test vectors we follow guidance consistent with NIST numeric test practices and ISO standards for financial data handling.

This tool is informational only. It is not a substitute for legally binding loan disclosures. For regulatory guidance and dispute resources, consult your local consumer protection authority.

Worked examples

Example 1: $20,000 principal, 5.0% APR, 10 years, 12 payments per year; the calculator returns monthly payment, total paid, and total interest.

Example 2: $50,000 principal, 4.5% APR, 15 years, 12 payments per year; use this to compare the cost of longer terms versus monthly affordability.

F.A.Q.

Does this calculator handle variable interest rates or income-driven repayment?

No. This tool models a fixed-rate amortizing loan only. Variable-rate loans and income-driven plans change payment or principal behavior and require specialized calculators or official servicer projections.

How are extra payments or prepayments handled?

This calculator does not recalculate amortization or shortened term when adding extra principal payments. For accurate payoff timing with extra payments, use an amortization schedule calculator or an advanced planner that models prepayments.

What is the difference between APR and the periodic interest rate used here?

The APR is the annual percentage rate entered by the user. The periodic rate used in the formula equals APR divided by payments per year (APR/100/payments_per_year). This calculator does not include additional fees in APR; use the disclosed APR from your loan agreement.

How accurate are the results?

Results use standard double-precision arithmetic consistent with IEEE 754. Displayed currency values are rounded to two decimals. Small rounding differences can occur compared with lender systems that apply different rounding rules, day-count conventions, or include fees.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: 1bc38def0f7a

What changed (latest)

v1.0.0 • 2025-11-09 • 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 9, 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 • 2025-11-09 • 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: f17b96b38dd8