Who is behind this
Countworthy is built and maintained by Sohail Shah at MashxLabz, a hands-on software academy and studio. Sohail writes the formulas, cites the sources and answers hello@countworthy.com; every calculator’s math is re-derived independently before it ships. The same habits we teach — cite your sources, show your work, test your output — are the ones these pages are built with.
How every calculator is verified
A calculator you can't check is just a guess with buttons. So every tool on this site follows the same rules: The full write-up, including the one failure our tests cannot catch and what we built instead, is on the methodology page.
- The formula is shown on the page, in full, next to the calculator that uses it — never hidden behind the result.
- Every real-world number is sourced. Platform fees, revenue shares, withdrawal charges, formula coefficients: each one links to where it came from (official help pages, published studies, primary data), at the claim or in the page's audit trail.
- Worked examples are computed independently. Before a page ships, its examples are re-derived by hand and cross-checked against the page's own code, to the cent.
- Every page carries a "Formula last verified" date. Fee structures and benchmarks change; the date tells you how fresh the numbers are. When a platform changes its fees, the date resets only after we've re-checked against the source.
- The math is tested and independently re-derived. Every money and fitness calculator's formula is mirrored in a plain-Node golden test kept with the source and re-run on every formula change; the DRIP calculator has additionally had three independent line-by-line rebuilds, the third on 2 September 2026, and on that date the FIRE calculator's two worked examples were cross-checked against an independent simulation. Each page's "Formula last verified" line records what was checked.
- Everything computes in your browser. No signup, no uploads, your inputs are never stored — see the privacy policy for the whole (short) story.
Founders
Countworthy is co-founded by Sohail Shah, who builds and maintains it day to day (see above), and Shahbaz Rehman, a founding member of MashxLabz who holds a master’s degree in statistics and is pursuing his PhD. Both are based in the Greater Toronto Area.
To reach either of them, write to hello@countworthy.com.
What these tools are — and aren't
These are information tools: they do arithmetic honestly and show their work. They are not financial, medical, tax or legal advice, and no calculator knows your situation. The investing tools model assumptions you choose; the fitness tools estimate from published formulas, and each page states their limits. Where an input combination produces numbers with no real-world meaning, the tools say so instead of printing them confidently.
Found something wrong?
If a number looks off, a fee has changed, or a formula disagrees with a source you trust — tell us, and include the inputs you used. Accuracy reports are the most valuable mail we get.
Contact: hello@countworthy.com
How this site is paid for
Countworthy is free to use. There is no display advertising, no ad network, and no affiliate links yet. If a tool page ever carries one, it will be a labelled text link below Related tools, kept out of every calculator panel and every source citation, and it will never change a number, a default or a verdict. The full disclosure is at /privacy#affiliates.