Fidamen

Student Loan Amortization Calculator with Bi-Weekly Payments

This calculator models loan amortization under different payment frequencies, with a primary focus on bi‑weekly schedules (26 payments per year). It supports additional per‑period or annual extra payments and provides an apples‑to‑apples interest and payoff time comparison versus monthly payments.

Results are numerical estimates produced by closed‑form formulas and algebraic inverses of the annuity formula. Iterative amortization, rounding rules applied by your servicer, or special plan rules (for example, federal income‑driven repayment, forgiveness, or capitalization differences) may change real outcomes; see accuracy notes and citations below.

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

Governance

Record a9e42d46848a • Reviewed by Fidamen Standards Committee

Calculates monthly and bi‑weekly scenarios using the same principal, rate, term and extra payments and reports interest and time differences.

Inputs

Advanced inputs

Custom frequency

Results

Updates as you type

Monthly payment (with extras)

$212.13

Biweekly payment (with extras)

$97.82

Total interest — monthly

—

Total interest — biweekly

—

Interest saved (monthly − biweekly)

—

Payoff time difference (years)

—

OutputValueUnit
Monthly payment (with extras)$212.13USD
Biweekly payment (with extras)$97.82USD
Total interest — monthly—USD
Total interest — biweekly—USD
Interest saved (monthly − biweekly)—USD
Payoff time difference (years)—years
Primary result$212.13

Visualization

Methodology

We compute periodic rate = APR / periods_per_year, scheduled payment from standard annuity formula, then convert user extras into an equivalent per‑period amount. When extras increase the periodic payment, the number of payments to payoff is computed by inverting the annuity relation (or dividing principal by payment for zero interest).

For comparisons we calculate both scenarios with identical principal, APR and term, and report total interest and estimated payoff time. When the servicer applies different compounding or rounding rules, results will vary; the tool reports conservative, algebraic estimates rather than a servicer’s official payoff quote.

Key takeaways

Use the bi‑weekly method to see how 26 payments/year compares to monthly schedules. Enter extra per‑period or annual amounts to evaluate their effect on payoff time and total interest.

For official payoff numbers, request a servicer payoff statement. This tool follows standard financial formulas and includes conservative numeric checks; actual servicer posting and plan rules can change outcomes.

F.A.Q.

Does making bi‑weekly payments always save interest?

If bi‑weekly payments total the same annual amount as monthly payments, simple timing differences alone may produce modest savings; larger savings occur when bi‑weekly results in more frequent payments that reduce average daily balance. This calculator assumes identical APR and compounding; servicer rounding and how the servicer posts payments also affect actual savings.

Are the results exact payoff quotes?

No. These are algebraic estimates. Servicers may post payments, apply rounding, charge fees, or have specific rules for extra payments that change the payoff schedule. For a binding payoff amount, request a payoff statement from your servicer.

Can I model one‑time lump sums or changing payments?

This version converts annual lump sums into equivalent per‑period amounts. Modeling arbitrary changing payments or scheduled lump sums at precise dates requires iterative amortization and a date calendar; use a servicer payoff quote for exact timing effects.

How accurate is the calculator and what safeguards are used?

We use closed‑form financial formulas and algebraic inverses. Numeric safeguards guard against division by zero and invalid log arguments. Accuracy is subject to floating point limits; results are intended for planning and comparison, not legal payoff statements.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: a9e42d46848a

What changed (latest)

v1.0.0 • 2025-11-23 • 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 23, 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 • 2025-11-23 • 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: 56bf09a54090