Three calculators that answer the questions every race plan starts with: what your fitness predicts, what paces to train at, and what a goal time asks of each leg. They run on the same math the Endurance by Design app uses, so the numbers here are the numbers your plan would be built on.
Enter one recent race. See the predicted time and pace for 5K, 10K, half marathon and marathon, plus the threshold pace your training should hang off.
Five running zones from a threshold pace, a recent race or a goal time. Add your FTP for bike power zones and a swim time trial for critical swim speed.
A goal time becomes swim, T1, bike, T2 and run splits with the pace each needs. Or add your paces up to a finish. Sprint, Olympic, 70.3 and 140.6.
Each calculator mirrors a rule from the Endurance by Design plan engine: the 1.06 exponent that projects one result to another distance and to a one-hour threshold effort, the five threshold-anchored run zones, the FTP zone midpoints, and the swim, bike and run shares of a triathlon finish. A result you get here is a result the app would agree with, which is the point of showing it. The science page explains where each rule comes from.
Updated October 21, 2026
Endurance by Design builds a periodized plan backward from your race date with your paces on every session, then adapts it to how training actually goes. Free to download on the App Store, with a 7-day free trial.
