Our Methodology

Stage 1 — Source Research

Before any code is written, we identify the canonical formula and the strongest available source for it. The hierarchy we use, from most preferred to least:

1. Primary government code or regulation. National Electrical Code (NEC) for electrical math, IRS tax tables for federal tax calculators, NFPA fire code for safety-critical numbers.
2. Government-published reference data. CDC growth charts and BMI ranges, NIH/NIDDK metabolic equations (e.g., Mifflin-St Jeor for BMR), Federal Reserve data for inflation calculators, USDA dietary guidelines for nutrition.
3. Recognized professional or industry standards body. ANSI E1.2 for entertainment trussing, IEC 61938 for audio phantom power, IEEE for engineering math, ISO for acoustics, Art-Net specification for entertainment networking, AVIXA for AV display standards.
4. Peer-reviewed academic publication. Original Sabine paper (1900) for reverberation time, original Mifflin et al. (1990) paper for BMR, etc.
5. Manufacturer-published reference data. For calculators that depend on equipment specifications (e.g., LED panel power consumption, projector throw ratios), we use values published in spec sheets from category-leading manufacturers — Daktronics, Christie, Barco, d&b audiotechnik, etc.

The source we used is displayed in a citation block below the formula on every calculator page, with a clickable link to the original document. If you can't verify a number we display by following the source link, that's a bug — please report it.

Every formula across the site is also collected in one place — our complete formulas reference — so you can scan the math for every calculator without having to open each page individually.

Stage 2 — Implementation

Calculator math is implemented as pure functions in TypeScript, kept entirely separate from any user interface. This separation matters for two reasons:

• Testability. Pure functions can be unit-tested against known inputs and outputs without rendering any UI. A test suite covering 210+ cases runs on every code change.
• Auditability. The math you see in our "step-by-step solution" sections matches the math executed in the function — they aren't parallel implementations that can drift apart.

All calculation runs in your browser, client-side. We do not transmit your inputs to a server, store them in cookies, or use them for analytics. You could disconnect from the internet after a calculator page loads and the calculator would continue to work.

Stage 3 — Automated Testing

Every calculator has accompanying unit tests that verify:

• Known-answer correctness — at least 3 hand-verified test cases per calculator, often more.
• External cross-check — outputs compared against at least one independent reference tool. For finance: CFPB's consumer mortgage calculator, Bankrate, IRS tax tables. For health: CDC BMI tables, peer-reviewed BMR equations. For trades: manufacturer-published reference data.
• Edge case handling — zero inputs, negative numbers, non-numeric inputs, very large numbers, divide-by-zero scenarios. Calculators must degrade gracefully (return "—" or a clear error message) rather than crash or display "NaN".

Tests are open-source friendly: the entire test suite runs from a single command (npm test) and currently passes 210+ assertions across 7 categories of calculators. Test results are reviewed before any change is deployed.

Stage 4 — Manual Cross-Verification

Beyond automated tests, every new calculator is manually compared against at least two independent third-party tools or hand calculations before launch. The discrepancy threshold is rounding tolerance — typically less than 0.5% on the result, depending on the calculator type. Anything outside tolerance is investigated and resolved before launch.

Examples of cross-verification we've actually done:

• Mortgage calculator — verified against CFPB's consumer.gov calculator, Bankrate, and hand-calculation using the standard amortization formula.
• BMI calculator — verified against CDC's adult BMI calculator and the WHO reference tables.
• TDEE calculator — Mifflin-St Jeor implementation matched against the original 1990 paper's sample calculations within 1 calorie/day.
• Pythagorean / quadratic / standard deviation — verified against Wolfram Alpha and Khan Academy reference solutions.
• LED wall power — verified against published spec sheets from Daktronics, Absen, ROE, and Unilumin for panel-watts × count math.

Stage 5 — Maintenance & Updates

Every calculator displays a "Last reviewed" date near the top of the page. We update calculators when:

• The underlying authority publishes a revision (e.g., NEC publishes a new code edition, IRS releases new tax tables, CDC updates BMI ranges).
• A user reports a discrepancy via the "Report an error" link.
• Routine review cycles — quarterly for YMYL (Your Money / Your Life) content, annually for stable math content.

For finance and health calculators specifically, we follow Google's YMYL guidelines for content quality: visible last-reviewed date, clear sourcing, named editorial responsibility, and visible disclaimers reminding users when professional consultation is required.

Authoritative Sources We Use

A non-exhaustive list of the primary sources cited across our calculators:

What We Don't Do

For full transparency:

• We don't accept paid placements inside calculator content. No "sponsored by" calculator results, no advertiser-influenced default values.
• We don't sell or share user data. Calculator inputs never leave your browser.
• We don't use AI-generated math without human review. Calculator implementations and step-by-step explanations are written and reviewed by humans before publication.
• We don't hide formulas behind paywalls. Every formula and source is visible on every page, free, no email required.
• We don't replace professional advice. For YMYL content (financial, medical, structural, electrical), we display visible disclaimers and recommend qualified professional consultation when appropriate.

How to Report an Error

Every calculator page has a "Report an error" link that opens a pre-filled email to contact@calqpro.com. Please include:

• The calculator URL.
• The exact inputs you used.
• The result you got from us.
• The result you believe is correct, with a source link if possible.

We typically respond within 2 business days. If a calculator is found to have a math error, we ship a correction within 1 week and document the change in our git history (commits are public on GitHub).

Open Source Transparency

All calculator math is publicly viewable on GitHub. You can audit the formulas, file issues, and verify that what runs in your browser matches what's in our public source code. The calculation library lives at lib/calculators/ in that repository.

Page last reviewed: May 2026.