Calculation logic
Formula logic is isolated in TypeScript modules so the same math can power multiple interfaces and be reviewed independently from the page layout.
How we work
Every number is verified.
We validate every formula against peer-reviewed sources, cross-check results against reference implementations, and document the math so you can verify it yourself.
Last updated: March 2026
Rounding
Results are rounded for readability, but the calculator preserves precision during internal calculations wherever it materially affects totals.
Assumptions
Every calculator includes an assumptions section that explains what the tool does and does not model.
Privacy
The launch version computes results locally in the browser. If future features introduce saved scenarios or analytics events, those changes should be documented on-page.
01
Source verification
Formulas from authoritative sources only
Every formula is traced back to its origin — academic papers, government publications, or recognized industry standards. No secondary sources or guesswork.
✓ Academic papers — peer-reviewed publications for health, science, and engineering formulas.
✓ Government standards — IRS tax tables, WHO BMI classifications, and NIST measurement standards.
✓ Industry references — CFA Institute for finance, ACSM for exercise physiology.
02
Cross-validation
Every result verified against known answers
Each calculator is tested against reference data sets, known worked examples, and at least one independent implementation. Edge cases are tested explicitly.
✓ Reference data sets — tested against textbook examples with exact expected outputs.
✓ Independent verification — results compared against Wolfram Alpha, Excel, or domain tools.
✓ Edge case testing — boundary values, zeros, and extreme inputs handled gracefully.
03
Transparency
Show the math, cite the source
Every calculator page shows the formula, explains variables, and links to source material. Assumptions like rounding rules are stated explicitly.
✓ Formula display — the complete formula is shown with variable definitions and units.
✓ Source citations — direct links to source material for every formula.
✓ Stated assumptions — rounding rules and simplifications documented in plain language.
04
Ongoing maintenance
Formulas don't expire, but context does
Tax rates change. Guidelines update. We run automated checks and update calculators when underlying data changes. Each calculator shows when it was last verified.
✓ Automated regression — test suites verify every calculator still produces correct results.
✓ Version tracking — every calculator displays its formula version and last-verified date.
✓ Update monitoring — source material tracked for changes and updated proactively.
Worked example
How we verify a formula
Compound Interest Calculator
✓
Source formula A = P(1 + r/n)^(nt) — sourced from CFA Institute, Quantitative Methods.
✓
Reference test P=$10,000, r=7.5%, n=12, t=10 → Expected: $20,966.83. Our result: $20,966.83 — matches to 2 decimal places.
✓
Cross-check Verified against Wolfram Alpha, Excel FVSCHEDULE, and a Python reference implementation. All match.
✓
Edge cases Tested: r=0% returns principal, t=0 returns principal, n=1/4/12/365 all correct, large t=100yr precision maintained.
Editorial process
How each calculator goes from idea to published tool
Trace the formula to an authoritative origin
Every formula is sourced from peer-reviewed papers, government publications, or recognized industry standards. Secondary summaries are not accepted as primary sources.
Code the logic in an isolated module
Calculation logic is written in a standalone TypeScript module, separate from UI and content, so it can be tested and reviewed independently.
Test against reference data and independent tools
Each calculator is tested against textbook worked examples, reference data sets, and at least one independent implementation such as Wolfram Alpha or Excel.
Write the methodology, assumptions, and sources
The formula, variable definitions, rounding behavior, assumptions, worked examples, and source citations are documented on the calculator page.
Automated regression and source tracking
Automated test suites verify correctness on every build. When underlying data changes, such as tax rate updates, the affected calculators are updated and re-verified.
Questions about our methodology?
If you find an error, disagree with a source, or want to suggest a better formula — we want to hear from you.
Report an issue or suggest an improvement