Every run gets you closer
to your next PB.

Free, fast tools that answer the questions runners actually Google — pacing, heat, fueling — so you train smarter and race faster. No account, no tracking, no 2,000-word intro before the tool.

Summer essential

Heat & Humidity Pace Calculator

How much should you slow down today? Enter temperature and humidity, get your adjusted pace — with the science behind it.

 Race day

Marathon Fueling Calculator

How many gels, and when? Get a printable minute-by-minute fueling schedule for your marathon or half.

 Goal setting

Race Pace Calculator

Pick a distance and goal finish time, get the pace you need to hold — in miles and kilometers.

 Predictor

Race Time Predictor

Enter 2+ recent races and get predicted times fitted to your own fatigue factor — not a generic formula.

See all tools →

Why Run4PB?

Most running calculators are buried under ads or padded with SEO filler. Run4PB does the opposite: the tool loads first, works on your phone at 6 a.m. before a run, and explains its method in plain language below the results — so you can trust the number, not just copy it.

Also live: a pace percentage calculator, a treadmill conversion chart, and a printable pace band generator. See all tools.

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