Long-form pieces on the formulas, history, and design choices behind every Foliokit utility. Read them when you're curious why a number is the number, not just what the number is.
The word "percent" comes from Latin per centum — for each hundred. Five hundred years after Italian merchants put it on commercial ledgers, almost every percentage question still reduces to one of three formulas. Here they are, with the kind of examples you'll actually run into, and the three traps that catch almost everyone.
Read the articleIn 2003 a NIST employee gave us 90-day rotations and the special-character rule. In 2017 he publicly apologised. The math says he was wrong, and the math hasn't changed since. The plain-English version of password entropy, why length beats complexity, and what NIST actually recommends now.
Read the articleThe little badge at the top of every blog post is a single division. But the assumed reading speed varies by 50% between publications, your real speed depends on the subject, and the formula misses everything that makes reading slow. Plus the standard word-count benchmarks for essays, stories, and novels.
Read the articleIn 1994 a Toyota subsidiary needed to track auto parts. The new design they shipped held thousands of characters and could be read at any angle. Three decades later, every restaurant menu and Wi-Fi router has one. Anatomy, error correction, the special-format payloads, and the sticker scam most people haven't heard of.
Read the articleThe Body Mass Index was invented in 1832 by a Belgian astronomer who repeatedly insisted it was a population-level statistic, not an individual diagnosis. Two centuries later it's the first thing on every chart. What BMI captures, what it misses, and what clinicians actually use to evaluate metabolic health.
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