Fact-Check Policy

Last Updated: June 2026

TrustedCalcHub is committed to factual accuracy in every calculator formula, data figure, and piece of educational content we publish. This page explains exactly how we verify information before it goes live and how we correct errors when they occur.

Our Fact-Checking Process

All content on TrustedCalcHub goes through a structured verification workflow before publication:

Step 1 — Primary Source Identification

Every calculator formula or factual claim must be traced to a primary authoritative source before it can be published. We do not use secondary aggregators or unverified online sources as our sole reference. Primary sources we accept include:

  • Official government agency publications (NOAA, NAPA, FHWA)
  • Platform documentation published by the service itself (eBay Seller Center)
  • Peer-reviewed academic papers and engineering standards bodies (ASTM, AASHTO)
  • Official API documentation (Open-Meteo, National Weather Service)
  • Established engineering textbooks and reference tables

Step 2 — Cross-Verification

After identifying the primary source, we cross-verify the formula or figure against at least one independent reference. For calculator logic, this means running the formula against known published results (e.g., checking our asphalt tonnage output against published contractor reference tables) before considering the result acceptable.

Step 3 — Edge Case Testing

We actively test boundary conditions that real users encounter:

  • Mathematical edge cases: Zero values, maximum values, decimal precision, unit conversions
  • Date edge cases: Leap years (Feb 29), month-end dates, cross-year boundaries
  • Fee edge cases: Category caps, promotional rate limits, per-transaction fee stacking
  • Regional edge cases: Country-specific fee schedules, currency formatting differences

Step 4 — Independent Review

High-stakes calculators (particularly those involving financial calculations like our eBay Fee Calculator) undergo a final review by a second team member before publication, comparing results against real-world transaction records.

Per-Calculator Fact-Check Sources

Asphalt Calculator

  • Density standard (145 lbs/ft³): NAPA (National Asphalt Pavement Association) reference tables
  • Volume formulas: Standard engineering mathematics — length × width × depth in consistent units
  • Unit conversions: NIST Handbook 44 unit conversion factors

Bitumen Calculator

  • Mix density range (2,100–2,400 kg/m³): Asphalt Institute MS-2 Manual
  • Bitumen content ranges: Marshall Mix Design method (ASTM D1559)
  • Calculation methodology: Civil engineering standard road mix quantity formulas

eBay Fee Calculator

  • US fee schedule: eBay Seller Center — Final Value Fee rates (verified June 2026)
  • International fee schedules: eBay country-specific seller help pages (UK, AU, CA, DE, FR, IT, ES)
  • Store subscription discounts: eBay Stores overview page
  • Update frequency: Reviewed within 30 days of any announced eBay fee change

Half Birthday Calculator

  • Six-month calculation: Standard calendar arithmetic (Gregorian calendar)
  • Leap year handling: ISO 8601 date standards
  • Month-end compression (Aug 31 → Feb 28/29): Verified against standard calendar tools

Snow Day Calculator

  • Weather data: Open-Meteo API (sourced from NOAA National Weather Service NWS models)
  • School closure probability algorithm: Based on published research on school closure thresholds by US region
  • ZIP code geocoding: Standard US Census ZIP code centroid data

How to Report a Factual Error

If you believe any data, formula, or content on TrustedCalcHub is factually incorrect, please contact us with:

  1. The specific page URL and section containing the error
  2. A description of what you believe is incorrect
  3. If possible, a link to your source material

Email: contact@trustedcalchub.com — Subject: "Fact-Check Error Report"

We investigate all error reports within 2 business days. Confirmed errors are corrected within 5 business days, and a correction note is added to the affected page.

Correction Notice Policy

When a factual error is corrected on TrustedCalcHub:

  • The correction is made immediately upon confirmation
  • The "Last Updated" date on the affected page is updated
  • For significant corrections that may have affected real-world decisions, we add a visible correction note at the top of the page explaining what changed and when

Limitations

Despite our best efforts, we acknowledge these limitations:

  • Fee data can change without notice: eBay and other platforms occasionally update their fee structures. While we review fees at minimum annually, there may be a short period between a fee change announcement and our update.
  • Live weather data is external: Snow Day Calculator results depend on Open-Meteo's weather forecast accuracy, which is outside our control.
  • Regional variation in construction standards: Asphalt and bitumen density can vary by regional aggregate type. Our calculators use standard industry values that may differ slightly from local practice.

For critical engineering, financial, or safety decisions, always verify results with a certified professional.