Fidamen

Mortgage APR Calculator with Bi-Weekly Payments

This calculator estimates bi‑weekly mortgage payments, the likely time to payoff if you add recurring extra payments, and a conservative APR approximation that factors in one‑time fees. It also compares monthly and bi‑weekly schedules to show potential interest and time savings.

Results are estimates produced from standard amortization formulas. They are provided for planning and comparison only and are not a substitute for a formal Truth‑in‑Lending APR disclosure from a lender.

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

Governance

Record 060317ffd000 • Reviewed by Fidamen Standards Committee

Calculate standard bi‑weekly payment, effective number of payments given an optional extra payment per bi‑weekly period, total interest paid, and a conservative APR estimate that includes one‑time fees.

Inputs

Results

Updates as you type

Bi‑weekly payment (no extra)

$701.23

Bi‑weekly payment (with extra)

$701.23

Estimated number of payments until payoff

780

Estimated years to payoff

30

Estimated total paid

$549,959.48

Estimated total interest paid

$246,959.48

Conservative APR estimate

453.33%

OutputValueUnit
Bi‑weekly payment (no extra)$701.23USD
Bi‑weekly payment (with extra)$701.23USD
Estimated number of payments until payoff780payments
Estimated years to payoff30years
Estimated total paid$549,959.48USD
Estimated total interest paid$246,959.48USD
Conservative APR estimate453.33%%
Primary result$701.23

Visualization

Methodology

Bi‑weekly payment calculations use the standard amortizing loan payment formula applied to 26 periods per year. Where extra payments are entered, the calculator estimates the effective number of payments using the closed‑form relationship between payment, principal, and periodic rate.

APR is approximated by adding the per‑yearized impact of one‑time fees to the nominal annual rate. This gives a conservative, easy‑to‑understand approximation but is not a substitute for a lender's legally required APR calculation under applicable disclosure laws.

Worked examples

Example 1: $300,000 principal, 4.5% annual rate, 30 years, no extra payments. The calculator returns the bi‑weekly payment and the total interest paid under a standard schedule.

Example 2: Add $50 extra bi‑weekly. The calculator estimates a reduced payoff time and lower total interest using the effective number of payments formula.

F.A.Q.

Is this APR exact and legally binding?

No. The APR value shown is a conservative estimate intended for comparison and planning. Lenders calculate APR according to regulatory rules and may include different finance charges and timing assumptions. For a legally binding APR, rely on the lender's Truth‑in‑Lending disclosure.

Why do bi‑weekly payments save interest?

Bi‑weekly schedules create more frequent payments (26 per year) compared with monthly schedules (12 per year). Paying more frequently reduces the principal slightly faster between compounding periods, which can lower total interest and shorten the loan term when payment totals are comparable.

How accurate are payoff estimates when I enter extra payments?

Payoff estimates use a closed‑form mathematical formula that assumes payments are applied immediately at each period and interest compounds at the specified periodic rate. These estimates are accurate under those assumptions, but real‑world timing, escrow changes, or lender processing can alter results.

Should I rely solely on this calculator to make a refinancing decision?

No. Use this tool for quick comparisons and planning. For decisions involving refinancing or legal commitments, obtain written estimates and disclosures from lenders and consult a financial advisor if needed.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: 060317ffd000

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: bd2ad9b76874