Estimate your IM 140.6 time after an IM 70.3

Many tools (calculators / estimators) based on past results give us coefficients to estimate our paces and estimated times on marathon or half marathon according to our time on a 5k or a previous10km. These tools have decades of results tables and analysis to give a good coefficent and they are therefore fairly accurate (when the race is going well for the athlete).


In my article ” Calculate your running paces“, the calculator gives you your paces for your trainings but it also gives you your estimates time on a 5km, 10km, 21km, 42km according to a performance already achieved. It is of course important to increment a true value (official time of the race, not the time you think you can do or the one that your watch displays without the pauses made during the race).


Now that triathlon is getting older, results tables are emerging and we are beginning to have several years of data on athletes and their performances on IM 70.3 and IM 140.6. Ironman races even organize an IM 70.3 and an IM 140.6 at the same place, where the course is simply doubled (2 swim loops, 2 bike loops and 2 running loops to make from an IM 70.3 an IM 140.6 ). The advantage is that the comparison is fairly reliable with a course that does not vary from one race to another (road surface, distance, elevation) the only variable here is the weather; Wind, rain, heat; (Same variable with all estimators / calculators).

Two methods are used to estimate your time IM140.6 from your IM 70.3 time.

A / The simplest, is the multiplier coefficient: min = 2.101 / standard = 2.167 / max = 2.234


Minimum time on IM 140.6 = Time IM 70.3 x 2.101
Most likely time on IM 140.6 = Time IM 70.3 x 2.167
Maximum time on IM 140.6 = Time IM 70.3 x 2.234


B / Estimating each sport individually (swim / bike / run), This method does not include transitions.

Allure IM 70.3 – 4 ” / 100m
Allure bike IM 70.3 – 2.52km / h
Running allure IM 70.3 + 31’’.7′ / km

To automatically calculate here is an Excel worksheet:


Download the file

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