Which running calculator do you need?
- Setting a race goal: the race time predictor turns a recent result into targets for other distances, and the split calculator turns the goal into times for every marker.
- Checking a run: the pace calculator works out pace, time or distance from the other two.
- Training by effort: the heart rate zone calculator sets your five zones.
- Tracking fitness: the VO2 max calculator estimates fitness from a race and shows what it is worth at other distances.
- Running indoors: the treadmill pace converter turns belt speed and incline into pace.
- Fueling: the running calories calculator estimates the energy a run costs.
Kilometers or miles
Every running tool works in either unit. Pick one once and the other tools open in the same unit next time, because the choice is saved in your own browser. Switching units converts the numbers already typed in, using 1 mile = 1.609344 km.
How far to trust a prediction
Race predictions and fitness estimates come from equations fitted to real performances, and they work best between similar distances run in similar conditions. The biggest gap is the marathon: predictions from short races are often too fast for recreational runners, so treat them as a best case. Each tool explains its own limits and links to the research behind it.