About Will Henschell and Greatest Calculators

• Tested formula modules. Every calculation lives in one of 43 self-contained modules, separate from the page, so the math can be tested directly. They are covered by 411 automated tests that run before any change goes live.
• Research before code. A new calculator starts as a research file: the official sources, the rules that apply, and the questions the page has to answer. The code comes after.
• Independent review. Before a new calculator is released, a separate review pass re-checks its formula and sources against that research file.
• Daily source watch. Every morning an automated job re-reads the official fee, price and tax pages behind the seller-fee, AI-cost and tax calculators, and flags any number that no longer matches what the calculator uses.
• Dated notes. Calculators built on numbers that change say when those numbers were last verified, so you can see how fresh the answer is.
• Content checks. 16 automated checks enforce structural and editorial rules, including one that blocks fake reviewer and fake advisor language.

Calculations run entirely in your browser. Your inputs are not sent to a server, stored, or logged. Formula choices, rounding and known limitations are documented in the calculator methodology; how content is written, sourced and corrected is in the editorial policy.

• LinkedIn
• GitHub
• Greatest Ventures LLC

• Greatest File Tools: Free, browser-based file utilities: compress and convert images, and merge, split or shrink PDFs, without uploading anything.
• Company Valuation Lab: Turns public SEC filings into interactive financial models, company comparisons and transparent valuation analysis.

70 calculators and 16 direct unit-conversion pages across 10 categories: Finance, Health, Construction, Cooking, Unit Conversion, Time & Date, Automotive, Business, Technology & Engineering, and Everyday Tools. Between them they answer 374 documented questions.

Each calculator page shows its inputs, its result, the assumptions behind that result, and the related tools worth using next.

Greatest Calculators is owned and operated by Greatest Ventures LLC, the company I run my projects through. I am the single named person accountable for every formula, assumption and correction on this site.

Questions, corrections, and calculator requests go to questions@greatestcalculators.com.

Greatest Calculators does not provide personalized financial, medical, legal, tax, or construction advice, and no result here should be treated as a substitute for a qualified professional who knows your situation.

All 46 finance and health calculators on this site carry a visible disclaimer stating the limits of their estimate. The site does not publish reviewer names, credentials, or endorsements it cannot substantiate — see the editorial policy for how that is enforced.

If a formula looks wrong, an assumption is unclear, or a result does not match what you expect, please report it. Include the calculator URL, the values you entered, the result you expected, and the result you saw.

Corrections are the fastest way this site improves, and I read every one. Send them to questions@greatestcalculators.com or through the contact page.