Free running tools
Calculators to pilot your training. MAS (vVO2max), pace, heart rate zones, race time prediction and more.
MAS calculator
Estimate your Maximal Aerobic Speed (vVO2max) from a race time and get your training paces.
Pace calculator
Convert running pace and speed (km/h, min/km, min/mile, mph). Pace conversion table included.
Heart rate zones calculator
Calculate your 5 HR zones with the Karvonen method or % of Max HR. Get your Z1 to Z5 in bpm.
Race time predictor
Estimate your race times on 5K, 10K, half marathon, and marathon from a recent performance.
Pace strategy (PacePro)
Plan your race pace segment by segment based on the elevation profile of your course.
Why use a running calculator?
Training by feel works for a while, then it stops. To progress, you need numbers you trust: a pace that matches your fitness, heart rate zones that match your physiology, and goals that match your real ceiling. That's what these calculators give you. They turn a single race time into a full picture: your aerobic ceiling (MAS / vVO2max), the paces you should hold for each session, the HR thresholds for hard versus easy days, and a realistic prediction for your next race.
All these tools are free, instant, and don't require a sign-up. They're built on the same training science used by coaches: Karvonen for heart rate, Daniels' VDOT for race prediction, MAS percentages by distance for pace estimation. The maths are honest, the assumptions are documented on each page.