Fidamen

Home Loan Payment Calculator with Bi-Weekly Payments

This calculator estimates mortgage payment amounts and payoff outcomes for bi‑weekly payment schedules and compares accelerated bi‑weekly (half of the monthly payment every two weeks) versus standard monthly payments. Use it to understand how changing payment frequency or adding a fixed extra amount affects total interest and loan duration.

Results are generated from standard amortization formulas and closed‑form estimates. They are intended for planning and comparison; exact payoff schedules depend on loan contract specifics, payment posting dates, and lender processing rules.

Updated Nov 30, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 93493390f007 • Reviewed by Fidamen Standards Committee

Calculates the bi‑weekly payment from annual rate, term, and principal. Estimates payoff schedule when a fixed extra amount is applied to each bi‑weekly payment using closed‑form amortization formulas.

Inputs

Results

Updates as you type

Scheduled bi‑weekly payment

$621.48

Bi‑weekly payment (including extra)

$621.48

Estimated number of payments (with extra)

780

Estimated years to payoff (with extra)

30

Estimated total interest (with extra)

$184,753.30

OutputValueUnit
Scheduled bi‑weekly payment$621.48USD
Bi‑weekly payment (including extra)$621.48USD
Estimated number of payments (with extra)780payments
Estimated years to payoff (with extra)30years
Estimated total interest (with extra)$184,753.30USD
Primary result$621.48

Visualization

Methodology

Calculations use periodic interest rates derived from the annual nominal rate and standard amortization formulas. For bi‑weekly calculations the year is modeled as 26 equal payment periods; for monthly calculations the year is modeled as 12 equal payment periods.

When a recurring extra payment is specified, the calculator estimates the number of payments and interest using closed‑form algebraic formulas for a fixed payment amount. For full amortization schedules or irregular extra payments, use an amortization table or consult your lender for an exact payoff statement.

Worked examples

Example 1: $300,000 principal, 3.5% APR, 30 years. Bi‑weekly scheduled payment is computed using 26 periods per year; accelerated bi‑weekly (half of monthly payment every 2 weeks) will typically shorten the term and reduce interest.

Example 2: Adding $50 to each bi‑weekly payment reduces the number of payments required and lowers total interest; this calculator provides an estimated payoff date in years.

F.A.Q.

Is a bi‑weekly plan always better than monthly?

Accelerated bi‑weekly approaches usually shorten the loan term and lower interest compared with identical total monthly payments because you make an extra month of payments each year. The magnitude depends on rate, term, and whether extra amounts are applied to principal. Check your lender's terms and payment posting rules.

Are these numbers exact?

These are estimates based on standard amortization formulas. Exact amounts can differ due to rounding rules, payment timing, escrow changes, fees, and lender processing. For an exact payoff schedule request a payoff statement from your servicer.

How does a zero interest rate behave?

If the annual interest rate is zero, the formula reduces to dividing principal by the number of periods. The calculator's closed‑form amortization formulas assume a positive rate for log/power expressions; for zero rates results are computed by direct division where supported.

Can I use this for irregular extra payments or lump sums?

This tool only models a fixed recurring extra payment applied every period. Irregular or one‑time lump sums require a full amortization schedule or simulation to capture exact payoff timing.

Sources & citations

Further resources

External guidance

Versioning & Change Control

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

Record ID: 93493390f007

What changed (latest)

v1.0.0 • 2025-11-30 • 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 30, 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 • 2025-11-30 • 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: 6887453f09a0