The latest articles on DEV Community by Mercenary For Hire (@mercenary_forhire_87885c). https://dev.to/mercenary_forhire_87885c https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4069447%2Fcf0d2b40-3196-4165-bb28-401c69da51df.png https://dev.to/mercenary_forhire_87885c en Mercenary For Hire Sun, 09 Aug 2026 03:51:07 +0000 https://dev.to/mercenary_forhire_87885c/raphaatlascom-4c67 https://dev.to/mercenary_forhire_87885c/raphaatlascom-4c67 <p>Most online calculators bury a 20-line formula under a megabyte of ad scripts and a 2,000-word SEO essay. I wanted the opposite, so I built RaphaAtlas (<a href="https://raphaatlas.com" rel="noopener noreferrer">https://raphaatlas.com</a>) — a hub of health calculators that are self-contained, framework-free, and load instantly.</p> <p>Why vanilla JS</p> <p>Every calculator is a single HTML file with no external dependencies. No React, no build step, no CDN calls. A macro calculator doesn't need 300KB of framework to run three arithmetic operations. The payoff is sub-second loads and pages that work even with JavaScript half-broken.</p> <p>The interesting math</p> <p>Two examples that were more nuanced than expected:</p> <p>BMR for the macro calculator. I implemented dual formulas — Mifflin-St Jeor and Katch-McArdle — because they diverge sharply once body-fat percentage is known. Mifflin uses weight, height, age, sex; Katch-McArdle uses lean body mass. For lean, muscular users the difference in daily calories is large enough to matter, so the tool switches based on available inputs.</p> <p>The Widmark equation for BAC. Blood alcohol estimation looks simple — BAC = (alcohol grams / (body weight × r)) − (β × hours) — but the distribution ratio r and elimination rate β vary by sex and individual, and the standard-drink definition changes by country. I built a jurisdiction selector so the "legal limit" reference and standard-drink grams adjust per region, and I front-loaded the safety framing hard: an estimate is never permission to drive.</p> <p>What I'd tell anyone building calculator tools</p> <ul> <li>Show the formula. Users trust a number more when they can see how it's derived, and it's a genuine differentiator against black-box competitors.</li> <li>Structured data pays off — JSON-LD on the tool pages makes them eligible for richer search treatment.</li> <li>Ship the explanation as progressive disclosure: calculator first, "how this works" collapsible below. Don't make people scroll past an essay to reach the tool.</li> </ul> <p>RaphaAtlas is early and I'm adding calculators regularly. If you've built utility tools, I'm curious how you handle the tension between SEO content depth and keeping the actual tool front-and-center.</p> webdev javascript healthtech buildinpublic