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.
Race Time Predictor
Enter one race result and predict equivalent finish times across 1K to marathon. Uses the Daniels-Gilbert formula.
Training Pace Calculator
How slow should easy runs be? How fast is threshold? Derive all five Daniels training zones from a single race result.
Heart Rate Zone Calculator
Find your five training heart rate zones using Karvonen, LTHR, or MAF — and calculate your heart rate reserve.
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.
Race Strategy Calculator
Build a conservative-to-aggressive pacing plan from your race fitness level, using a recent race result or your activity data.
Running Calorie Calculator
How many calories does a 10K burn? Enter weight, distance, and pace to see total burn with a carb and fat breakdown.