Calculation methodology

A visible calculation model

Each calculator states its formula and keeps assumptions visible beside the inputs. Platform defaults are starting values rather than hidden facts, and users can override rates to match their market, category and account.

Versioned rules and sources

Platform-specific presets are stored separately from calculation code with a source URL, effective date and verification date. A new rule receives a new version instead of silently overwriting the historical assumption.

• Official pricing and policy pages are the primary sources.
• Automated monitors detect source changes but do not publish fee changes without review.
• Representative test cases compare expected results before deployment.

Rounding and currency

Internal calculations use JavaScript numeric precision and round only for display unless a carrier rounding rule is an explicit input. Currency selectors format values; they do not perform foreign-exchange conversion.

Testing and release process

Every calculation function is tested independently from the page interface. Tests cover a normal worked example, zero or boundary values and combinations that commonly expose fee-order or percentage-base errors. Before release, the English and Chinese pages are generated from the same typed calculator definition so formulas and defaults cannot silently diverge between languages.

A production build must pass type validation and the calculation test suite. We then inspect representative pages at desktop and mobile widths, check structured data, internal links, language alternates and the generated sitemap before deployment.

Worked examples and editorial review

Worked scenarios are written to explain the decision represented by each output, not merely to repeat the formula. Example defaults are illustrative and are never presented as a promise that they match a particular seller account. Each tool also identifies common mistakes and a pre-decision checklist reviewed by the SellerCalc editorial team.

Substantive reviews update the visible review date. Minor spelling or layout corrections do not imply that an external platform rule was reverified.

What rule monitoring can and cannot do

Scheduled monitoring checks selected official source pages for availability and meaningful content changes. A change creates an alert for human review; it does not automatically edit a fee, formula or effective date. This prevents navigation changes, regional redirects and wording updates from becoming unverified calculator rules.

Monitoring cannot see account-specific contracts, logged-in dashboards, private notices or every regional variation. Users should therefore compare material estimates with the current terms shown in their own account and use the source links provided on each tool page.

Corrections

If a preset or formula appears incorrect, send the calculator URL, market, expected result and official source through the contact address. Confirmed corrections are tested and recorded with a new review date.