Methodology

Purpose and scope

Business Math Lab provides practical planning calculations and educational explanations for common business decisions: pricing and margin, inventory planning, workforce turnover cost, and customer acquisition and lifetime value. Every calculator is a planning tool built from figures you enter — it does not connect to your accounting system, apply a specific accounting standard, or replace professional review of numbers used for financial reporting, tax filing, or legal decisions.

Formula selection

When a formula is chosen or documented, sources are preferred in this order:

• Official standards, government material, and institutional documentation, where applicable.
• University or academically credible educational material.
• Recognized professional or industry-body references.
• Reputable technical documentation.
• Direct mathematical derivation, for elementary formulas such as profit margin, markup, or gross margin.

Some business metrics — inventory carrying cost, customer acquisition cost, and customer lifetime value are common examples — do not have a single universal definition. Where a definition varies in practice, the relevant calculator page states which inputs, components, and assumptions it uses, rather than presenting one definition as the only correct one.

Variables, units, and time periods

Currencies are user-selected display labels, not automatic exchange conversion: enter every value already in your chosen currency, and the calculator formats the result in that currency without converting amounts between currencies. Percentages, time periods (annual, monthly, daily, or per-order), and other units are defined on each calculator page; a calculator does not silently convert between time periods or units on your behalf, so inputs need to share a consistent period and scope for the result to be meaningful.

Calculation precision and rounding

Calculations use the available numeric precision internally. Displayed results are rounded for readability at the moment they're shown, but intermediate values used to compute a result are not intentionally rounded before that final display step, unless a calculator explicitly states otherwise.

Worked examples

Every published calculator includes at least one worked example with real numbers, manually checked against the formula shown on the same page. Worked examples use internally consistent units and assumptions, and most calculators include a "Load example" button that loads the exact worked-example numbers into the form so you can verify the result yourself.

Validation and edge cases

Calculator formulas are implemented as pure, independently testable JavaScript functions, separated from form handling, formatting, and result rendering. Each calculator's automated test suite and manual review check:

• Missing or empty inputs
• Zero values, including division-by-zero cases such as zero revenue
• Negative values, and whether they're accepted or rejected per field
• Invalid or non-numeric input
• Unusually small or large values and non-finite results
• Percentage boundaries
• Rounding and unit consistency in the displayed result

Pages are also checked for mobile and desktop layout, keyboard interaction, and accessible error messaging before publishing.

Sources and citations

A calculator or guide gets a visible "Sources and methodology" section when its formula's definition genuinely varies across references, or when a specific, verifiable source materially shaped how the calculator interprets a term. Elementary arithmetic formulas — profit margin, markup, and gross margin, for example — are direct mathematical relationships and are not given an external citation just to appear more authoritative.

Review and corrections

If you report a formula or calculation error through the Contact page, it's investigated against the methodology described on this page and the calculator's documented formula and worked example. Confirmed substantive errors are corrected promptly, and the page's modification date is updated to reflect the correction — modification dates are not refreshed just to make a page look recently updated. See the Editorial Standards page for the full publishing policy.

Software and AI assistance

Software and AI-assisted tools may be used during drafting, testing, editing, or quality assurance. Published formulas, worked examples, limitations, and final page content are reviewed before release.

Contact

Questions about methodology, or a calculation issue to report? Visit the Contact page or email smartulethtb@gmail.com directly.