FirePlanIO

Editorial Standards

Last reviewed: September 2026

FirePlanIO publishes financial calculators and guides. Because readers make real money decisions with these numbers, every formula, table, and scenario on this site follows the verification process below. This page explains exactly how our math is checked, how often content is reviewed, and how to report an error.

How every formula is verified

Each calculator implements a standard, publicly documented financial formula — never a proprietary black box. Before a calculator ships, its output is verified in three steps:

  1. Source check. The formula is confirmed against established public references, including Investopedia (compound interest, amortization, the 4% rule) and the Consumer Financial Protection Bureau (CFPB) (mortgage amortization and loan disclosure rules).
  2. Independent recomputation. Worked examples are recomputed by hand or in an independent spreadsheet, and the results must match the calculator to the cent.
  3. Edge-case testing. Zero contributions, zero interest, very long horizons, and extreme rates are tested so the tool degrades gracefully instead of producing misleading numbers.

Where a model involves judgement — for example the 4% withdrawal rule or an assumed annual return — we state the assumption, its source, and its limitations directly on the page.

Update frequency

  • Calculators are reviewed whenever the underlying rules or tax-free limits change, and at least once per year.
  • Guides are reviewed on a rolling schedule and re-dated only after a substantive review, never automatically.
  • Scenario tables are regenerated whenever calculator logic changes, so the numbers in the articles always match the tools.

Corrections policy

If you spot an error — a wrong number, a broken formula, an outdated limit — please report it via the contact page or hello@fireplanio.com. Confirmed errors are corrected promptly, and material corrections are noted on the affected page. Reader corrections are a core part of how this site stays accurate.

Writing standards — no filler

Every article is written and edited in-house in English, reviewed by founder Y.W. Fung, and built around concrete, reproducible examples. We do not publish scraped, syndicated, machine-translated, or AI-generated filler content. If a paragraph does not help you make a better decision or reproduce a calculation, it does not belong on the page.

Independence and advertising

FirePlanIO is funded by display advertising. Advertisers have no influence over formulas, scenario results, or editorial conclusions, and we do not accept payment to alter calculator outputs. All tools are free, with no paywall and no premium tier.

Scope

FirePlanIO is an educational publisher, not a broker, lender, or registered investment adviser. Outputs are estimates for education and planning, not personalized financial advice. For advice about your specific situation, consult a certified financial professional.