Garmin Race Predictor: how does it work, is it accurate?

Garmin has a feature that predicts your finishing times for various race distances. How does this work? Can you trust the accuracy of Race Predictor? We attempt to explain all this and more.

What is the Garmin Race Predictor feature?

Race Predictor is a running feature that appears on quite a few Garmin watches. It attempts to quantify your ideal race times based on your fitness level. That way it provides you with a target to aim for. Predictions include 5K, 10K, half and full marathon race times.

This information can be viewed on the watch itself. For example, on the Forerunner 955 you can find it if you navigate to the Performance Glance. The default screen here is Vo2Max. Press the down button twice to view the predicted times. Each of the four distance times is displayed on a separate screen, along with a graph on how this has changed during the previous four weeks.

The info can also be viewed in Garmin Connect. Simply go to Performance > Race Predictor. Here you can also view stats for the past six months and one year. The procedure is the same on the web dashboard.

The obvious question is, how does Garmin come up with these figures?

The company does not reveal too much info on the actual calculations. According to their documentation, they utilize personal information (such as your age and gender), along with your Vo2Max estimate and recent training history to provide the target times. The watch needs several weeks of training data in order to come up with this targets. The more exercise history data, the better. This is not a static figure – rather, it will change over time.

The recent crop of watches have something Garmin refers to as “improved race predictor”. Previously it was a more simplified version of the feature that is not as accurate as it only takes into account Vo2Max. With just Vo2Max, the watch will typically estimate much faster long distance race times (unless you run a high volume with some fast long runs). Now your training history is taken into account.

Which devices are compatible with Garmin Race Predictor?

Garmin does not publish a comprehensive list of watches that support the Race Predictor feature. But we’ve looked through the individual specs on Garmin’s website.

Of the current devices in the Forerunner range (Forerunner 45 and above), all watches have the feature apart from the base Forerunner 45 model. The latest few generations of Fenix also have this as does the Epix and Enduro line.

However, you will not find Race Predictor on the Venu range, Vivomove, Vivoactive or Lily. The same is the case for Garmin’s line of fitness bands. So you could say the feature is reserved for Garmin’s higher-spec sports watches and outdoor watches, rather than general wellness devices and fitness bands.

Can you trust the accuracy of Garmin’s predicted times?

The more your train, the more accurate these Garmin predicted times will be. At least that’s the theory.

In reality, the accuracy of Garmin Race Predictor can vary quite a bit. For some people this is fairly close to the mark for others it is not.

There are those who find the figures are very generous and that they are unable to finish a race that quickly. Then there are those who find the figures under-estimate their actual abilities. They tend to be in the super-fast category.

Looking through comments on forums, it seems there are more people who belong in the overly optimistic race times camp. So don’t let unreacheable targets demotivate you as you might need to be very well trained to achieve them.

Heat and altitude acclimation might also be an influence. If you’re not fully adapted to your environment and fully rested – you will probably not be able to achieve anything close to those ideal times. Nutrition, attire and even your playlist can effect your actual finish time on a particular day!

Essential reading: Top fitness trackers and health gadgets

There are several things you can do in order to maximise the accuracy of Garmin Race Predictor. One of these is to go to your user profile and make sure the value setting for your maximum heart rate is correct. That’s because this info is used to work out your heart rate zones and estimate your Vo2max. It is also a good idea to run with a heart rate chest strap in order for your heart rate zones to be updated as your fitness improves.

If you have more than one Garmin watch or fitness tracker, make sure you have enabled the Physio TrueUp feature. This allows your device to sync your training history across multiple devices. As mentioned above, on newer watches a history of your workouts is also utilized to work out your predicted race times.

It is important to remember that this is not hard science. Rather it is just an estimate that the device on your wrist is attempting to make. While your running speed is directly proportional to your VO₂ max, these times do not factor in variables including weather on the day, course difficulty or training regimen. So take all this with a ladel of salt.

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