About Run4PB
Run for personal best — tools that respect your time as much as your training does.
Why this site exists
Every runner has done it: you just want to know how much to slow down in today's humidity, and instead you get a page with three pop-ups, an autoplay video, and 2,000 words of filler before the calculator. Run4PB is the opposite. The tool loads first, works on your phone at 6 a.m. before a run, and gets out of your way.
How the tools work
Every calculator explains its method in plain language right below the results — the formula, where it comes from, and its limits. You should be able to trust the number, not just copy it. If a tool ever gives you a result that doesn't match your experience, trust your body first; these are guides, not coaches.
Who makes this
Run4PB is built by one runner who codes — no content team, no SEO farm. It stays small on purpose: a handful of tools that each answer one real question well, added one at a time. See what's live and what's next on the tools page.
Everything here is general guidance, not medical or coaching advice. Race-day decisions are yours.