Free Running Calculators
Evidence-based tools for road runners, marathoners, and triathletes. Each calculator runs entirely in your browser — no account required, no data collected. Pace and prediction tools use the Daniels-Gilbert formula; heart rate zones use the Karvonen method.
Running Pace Calculator
Given any two of pace, time, and distance — get the third instantly. Works in kilometres and miles.
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Race Time Predictor
Enter one race result and predict equivalent finish times across 1K to marathon. Uses the Daniels-Gilbert formula.
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Training Pace Calculator
How slow should easy runs be? How fast is threshold? Derive all five Daniels training zones from a single race result.
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Heart Rate Zone Calculator
Find your five training heart rate zones using Karvonen, LTHR, or MAF — and calculate your heart rate reserve.
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Race Pace Calculator
Set a target finish time, split the race into phases, and get the required pace for each. Lock phases to hold specific paces.
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