Each calculator applies an accepted formula for its subject and states it on the page. Where several methods exist, the page names the one used. Results are mathematically exact for the inputs provided; they are estimates relative to the real world, which includes factors a calculator cannot capture.
Results are rounded to conventions normal for the subject — currency to the cent, percentages to one or two decimals, scientific values to appropriate significant figures. Worked examples never show fake precision.
Calculators involving physical measurements support U.S. customary and metric/SI units. Your unit choice is remembered for the session. We do not create duplicate indexable pages for metric and U.S. versions; the unit is an interaction, not a separate page.
Sources are reviewed before display. Unverified or fabricated citations are never published. Each record carries a last-reviewed date, and content that depends on changing rules is flagged for periodic review.
Financial calculators explain their assumptions and show formulas. Results may differ from a lender, bank or tax authority. Tax and regulatory tools record their data year and last-verified date; stale rules are flagged rather than silently presented as current. We never promise investment returns.
Health calculators identify the equation or method used and cite authoritative sources where appropriate. They are educational information only and not a substitute for professional medical advice. They do not diagnose conditions.
Bible calculators calculate from the texts and data you provide. Chronology tools cite the Hebrew (Masoretic), Septuagint and Samaritan traditions and name how they are reconciled. These tools are educational and devotional; they do not claim that calculations prove theological conclusions.
The Universe Probability tool keeps parameter sensitivity, fine-tuning, probability and philosophical interpretation distinct. It does not claim that scientific probability estimates prove God, which preserves scientific credibility.