About Ryutility

Ryutility is a small, independent collection of free web tools. The goal is simple: solve one specific, everyday problem per tool, load fast, work on any device, and get out of your way — no account required, no unnecessary clutter.

Ryutility grew out of more than a decade of recreational distance running — enough marathons, half marathons, and disappointing training blocks to get tired of pace calculators that were paywalled, cluttered with ads that broke on mobile, or just quietly wrong. The Training Zone Calculator was built first, using Jack Daniels' VDOT method, because after years of training against different systems, it's the one that held up best against what actually happened on race day — not the one that sounded the most sophisticated on paper.

Since then, Ryutility has grown into six calculators covering pace, race prediction, heart-rate zones, split strategy, and treadmill conversion, plus a growing set of Guides that go deeper into the reasoning behind the numbers: when to trust pace over heart rate, how to choose a pacing strategy for race day, and where formulas like Riegel's start to break down. The formulas aren't original — VDOT, Karvonen, and Riegel are all established, published methods — but the goal is to explain them the way a training partner would, not the way a textbook does.

Ryutility is built and maintained independently. If something is broken or you have a suggestion, see the Contact page.