Making predictions is fraught with error because of how our individual physiologies differ, says RW Scientific Editor Prof. Ross Tucker. Combine that with how training prepares us to go that much longer, and… well, we urge caution if you’re using a hard-and-fast predictor. Rather put the following formulas to work, to produce an estimated range for your Comrades finishing time, based on your best recent marathon time:

Lower estimate (fastest probable time) = T1 x D2 / D1 x 1.1

Upper estimate (slowest probable time) = T1 x D2 / D1 x 1.15

• T1 is your your best recent marathon time in minutes
• D1 is the marathon distance in kilometres
• D2 is the distance you want to predict a time for in kilometres (for Comrades, that’s 88km).

For example, if your marathon time is 4 hours, then your lower estimate is:

(4 x 60) x 88 / 42.2 x 1.1 

= 551 minutes

= 9:11

Your upper estimate is:

(4 x 60) x 88 / 42.2 x 1.15 

= 576 minutes

= 9:36

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