Methodology

Every formula on CalcLab is sourced from a peer-reviewed paper, government guideline, or vendor documentation. This page is the single index for our editorial standards and review process.

Editorial principles

• One primary source per formula. If we can't link a published paper or official guideline, we don't ship the tool.
• Expert review. Domain reviewers (RDNs for health, CFA charterholders for finance, licensed contractors for construction) sign off before launch and again annually.
• Transparency. Every tool ships a "How this is calculated" section that walks through the math.
• Accessibility. WCAG 2.2 AA. Keyboard navigable. Screen-reader tested.
• Performance. Sub-second time-to-interactive on a mid-range mobile device on 4G.

Formula sources by cluster

Health & Fitness

• BMR / TDEE — Mifflin-St Jeor (Mifflin et al., Am J Clin Nutr, 1990). Activity multipliers from the FAO/WHO/UNU 2001 expert consultation.
• Calorie deficit weight-loss timeline — 3,500 kcal/lb baseline (Wishnofsky, 1958) corrected with Hall's NIH Body Weight Planner adaptive thermogenesis curve (Hall et al., Lancet, 2011).
• Pregnancy weight gain — IOM/NASEM 2009 guidelines, current as of 2026 CDC and ACOG references.
• Macros — Acceptable Macronutrient Distribution Ranges (NASEM 2005). Keto cap from Volek & Phinney clinical literature.
• Peptide reconstitution — Standard volumetric dilution arithmetic. Tool does not provide medical advice.

Finance

• Mortgage amortization — Standard amortization-formula (M = P · r(1+r)ⁿ / ((1+r)ⁿ−1)) per CFPB regulation Z guidance.
• Compound interest — A = P(1+r/n)^nt with monthly contributions added at end-of-period.
• Margin / markup — GAAP standard definitions.

Construction

• Concrete volume — Volume = L × W × D. 1 yd³ = 27 ft³. Bag yields per Quikrete and Sakrete published spec sheets (60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³).
• Gravel & fill density — USDA / NRCS published densities (crushed stone 100 lb/ft³, pea gravel 105 lb/ft³, fill dirt 95 lb/ft³).
• Solar production — NREL PVWatts methodology, US average sun-hours by state from NREL TMY3 dataset.

Education

• GPA — Standard 4.0 scale. Honors +0.5, AP/IB +1.0 (College Board / IBO standard weighting).

Developer

• AI token costs — Public list pricing from Anthropic, OpenAI, and Google as of the page's last-updated date.

Review cadence

Every tool is reviewed at least annually. Tools tied to fast-moving inputs (AI token prices, solar tax credits, IOM guidelines) are reviewed quarterly. Each tool page lists its last review date.

Corrections

Spot a mistake? Email calc@3stf.com with the URL and the issue. We log every correction with a date and a public changelog entry.

Disclaimer

CalcLab provides tools for informational and educational purposes only. Nothing on this site is medical, legal, financial, or engineering advice. Consult a qualified professional for decisions that affect your health, finances, safety, or property.