Estimate a full-distance triathlon finish time from an Olympic-distance triathlon personal best and a standalone marathon personal best using a published study-cohort equation.
What This Predictor Uses
The predictor uses two published multiple-regression equations for recreational athletes. Both require an Olympic-distance triathlon personal best and a standalone marathon personal best. They do not use three independent swim, bike, and run times, and they do not predict a 70.3 result.
| Model | Equation in minutes | Study detail |
|---|---|---|
| Male cohort | 152.1 + 1.964 × Olympic PB + 1.332 × marathon PB | n = 126; R-squared = 0.65; standard error = 56.8 min |
| Female cohort | 186.3 + 1.595 × Olympic PB + 1.318 × marathon PB | n = 28; R-squared = 0.53 |
Worked Example
With a 2:30:00 Olympic-distance PB and a 3:30:00 marathon PB, the male-cohort equation gives 726.42 minutes, or 12:06:25.2. The female-cohort equation gives 702.33 minutes, or 11:42:19.8.
Reading the Model Details
R-squared describes how much variation the fitted model explained in its study sample; it is not an accuracy percentage for an individual. The male paper reported a 56.8-minute standard error of estimate. The calculator displays the estimate plus and minus that value as a reference band, not as a guaranteed confidence interval. No corresponding standard error is invented for the female equation.
Sensitivity to the Input PBs
Each five-minute change in an input moves the estimate by its coefficient times five. In the male equation, five minutes changes the Olympic term by 9.82 minutes and the marathon term by 6.66 minutes. The female changes are 7.975 and 6.59 minutes.
Assumptions and Limitations
The models are most defensible for recreational athletes reasonably similar to the original cohorts and using correctly matched prerequisite events. Course difficulty, weather, training status, equipment, transitions, nutrition, and time between performances are not represented. A prediction should guide planning, not replace current race-specific preparation.
Sources
Rüst et al., Personal Best Times in an Olympic Distance Triathlon and in a Marathon Predict Ironman Race Time in Recreational Male Triathletes, 2011. Rüst et al., Personal Best Times in an Olympic Distance Triathlon and a Marathon Predict an Ironman Race Time for Recreational Female Triathletes, 2012.
