How to time a triathlon

This article explains how to use RaceSplitter in the timing of multi-sport events like triathlons.

Build your race at

For a variety of reasons which we won’t detail here for the sake of brevity, you’ll want to create your race at and then download it to your device(s), as opposed to creating it directly in the app. For the rest of this article, we’ll presume you’re going to do that.


Setup the event as a “mass-start” race

RaceSplitter natively supports mass-start, interval-start and wave-start races. Interval and wave starts assume you’re starting each participant or wave on a fixed interval, e.g. every 30 seconds.

Although most triathlons are mass start, some organizers start their racers in waves. Even for those races, you’ll anyway likely want to setup the event as a mass-start race in RaceSplitter. Here’s why…

In a triathlon, given the liklihood of occasionally needing to time groups of racers arriving faster than would be possible to manually type in bib numbers (for example, in the swim/bike transition, before the racers have had time to get spread out), you’ll need the ability to create rapid-fire “bibless” timing entries for later correction. (Bibless timing entries are those you create by simply tapping the “Record” button without having first entered a bib number.) Bibless timing is only possible in mass-start RaceSplitter races.


But what if I start my racers in waves?

How do you time a wave-start event using a mass-start race type in RaceSplitter? You enable the “variable-start” setting on the race, and then time one additional split — the race start.

Variable-start support is provided through a combination of RaceSplitter (the app) and the online results services provided by In a mass-start race with the “variable-start” setting enabled, will assume that the race’s first split represents the race start for each participant, and then automatically subtracts that Split 1 time from each racer’s subsequent split times (including the finish).

To time a “wave” of racers starting in a RaceSplitter “mass-start” race, you’d pre-enter all the wave’s bib numbers onto the RaceSplitter timing bar and then tap “Record”, to assign them all the same time.


Disable “Auto-Split” mode

Let’s say you’ve timed racer 123 and a few minutes later see racer 132 coming along. But instead of typing “132” into RaceSplitter, you accidentally typed “123” and hit “Record”.

By design, RaceSplitter will assume you’re timing racer 123 a second time, and will add an additional lap to the race. That’s convenient when you have a multi-lap race, but it’s problematic in a scenario like the above.

To prevent RaceSplitter from creating additonal laps on the race when you accidentally time a duplicate bib number, you can (and should) disable the “Auto-Split” mode on the race.

When auto-split is disabled and you accidentally time racer 123 a second time, an entry will be created for the bib number “10123”, i.e. a bib number unlikely to exist in your start list and one you’ll later be able to recognize as a duplicate needing correction.


Number of devices

Next, you’ll need to consider the number of devices with which you’ll time the event. We discussed this at the beginning of the article, but let’s go over it again here.

Ideally, you’d have three—one device timing the swim/run transition, one timing the run/bike transition and one timing the finish. (And if your race is a wave-start, then as mentioned above, you’d also need to time one additional split, the race start.)

Both during the race and afterwards, each device can publish its recorded data to, and our website will combine all the results into a single set of race results that can be browsed and printed by split and by category. The benefit of publishing your data during the race, is that people can then follow the race’s progress as it unfolds at

With one device assigned to each split and auto-split mode disbled on the race, very few errors can occur.

But let’s imagine you want to capture all three splits, but only have two devices (or people) available to time the race. This is certainly possible and there’s two options for doing it, though you’ll certainly want to go for the second.


Option 1: A single race, enabling auto-split

The first option would be to enable auto-split mode on the device timing multiple splits. After timing the swim/bike transition, the same device and race could later be used to time the finish.

But this would be problematic for two reasons:

  1. Say you happened to miss timing racer 75 in the swim/bike transition. When you later timed them at the finish, RaceSplitter would insert that time into “Split 1”, the swim/bike split, since it wouldn’t find any record for that racer in that split.
  2. We’ve already discussed the second problem, and that is the creation of erroneous splits on the race when you accidentally time the same bib number multiple times.


Option 2: Multiple copies of the same race, on a single device

In this preferred option, you’d load your race twice on the device that’ll be timing two splits, and each race would, as discussed above, have auto-split disabled.

How do you load a given race multiple times? You definitely DO NOT do it by loading it once, and then duplicating it on the device. That second race would NOT be recognized by when its results are published.

Instead, load the race the first time by importing it from the download email you were sent by, and then change the race’s name on the device—e.g. from “My Triathlon” to “My Triathlon Swim/Run”. Then load the race a second time, again importing it from the download email you were sent by

When loading the race the second time, RaceSplitter will create a second copy of the race on your device. (If you hadn’t changed the name of the first race, however, your second import of the race would have overwritten the first copy; and that’s why you changed its name.)

With this setup, you’d time the swim/run transition with the first copy of the RaceSplitter race, and the event finish with the second—with each race in RaceSplitter publishing its results to, where they would get combined.


Starting the race clock in RaceSplitter

It would be ideal that all RaceSplitter clocks on all devices are started on time, i.e. when the race actually starts. But it’s only necessary that one of the RaceSplitter clocks are started on time.

Why? Because when results from multiple devices are published to, the website will use the earliest seen start time as the official race start time, and will adjust all other times accordingly.


Wrapping things up

So let’s wrap up what we’ve learned about timing a triathlon with RaceSplitter.

  • We’ll be creating the race at, and then downloading it to our various devices.
  • We’ll be setting up the race as a mass-start race, even if we have a wave-start event, so that we can create bib-less timing entries when necessary, and so that we can disable auto-split mode.
  • If we start our racers in waves, we’ll use the “variable-start” feature, supported at, and we’ll therefore also be timing the race start, in addition to the other splits.
  • We only need to make sure that one RaceSplitter race clock is started when the race actually starts.
  • RaceSplitter on each device will publish its collected data to, where the data will be combined into one set of race results, browsable by split and category.


Finally, and most important of all, we’ll be sure to simulate our event at least once using a practice race before the real race day!

Scenarios & examples


This article explains how to use RaceSplitter to time a triathlon.

Timing 5k and 10k races together

This article discusses the considerations involved in a common timing scenario—5k and 10k running races, ran together in a single event.

Variable start races

This article explains how to time races in which the start interval between participants or waves is variable.

Complex Multi-Race Event

This blog article explains how we organized the timing of a multi-day, multi-race and multi-split ultra event using RaceSplitter.

How to time ties & groups

This blog article explains how we organized the timing of a multi-day, multi-race and multi-split ultra event using RaceSplitter.

Complex Wave Starts

This article explains how we helped a customer setup timing for a complex wave-start event.

Relay Races & Team Events

This article discusses considerations related to timing relay races and team events.

Multi-heat regatta

This article discusses timing of a multi-heat boat regatta.

We’re here to help!

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