Strava’s AI Will Now Predict Your Race Times (but I'm Skeptical)

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Strava, the superstar running/cycling app, now has a subscriber-only AI feature that will predict how fast it thinks you could run a 5K, 10K, half-marathon, and marathon. The predictions use a different method from those you might see from other sources, though. 

For me, Strava's predictions look less accurate than the ones I get from Garmin and Runna, but the feature is too new to say for sure how accurate they will be for everybody else.

How to view your race predictions in Strava

Race predictions are only available to Strava premium members. That membership runs $11.99/month or $79.99/year and also gets you mapping tools and extra analytics, like goals and fitness scores. 

If you’re a premium member, you can find your predictions in the mobile app by going to the You tab (bottom right when you’re looking at the home screen), then tapping Progress at the top of the screen. Right underneath your weekly mileage, you’ll see your race time predictions. The feature is currently only available on mobile, not in the web app. 

To have enough data for a prediction, you need to have logged at least 20 run activities in the last 24 weeks, Strava says. The predictions will update after each run, and after three days without running. In addition to telling you how fast it thinks you can run right now, Strava's AI will also tell you how this compares to your predicted time from 30 days ago. The predictions assume that your race would be on flat ground in good weather. 

How Strava’s predictions compare to other apps and formulas

You may have seen race predictions before—for example, on your Garmin watch or on websites like vdoto2.com. Those usually use a mathematical formula, while Strava’s new predictions are powered by “Athlete Intelligence,” which the company describes as a machine learning (ML) model.

Here’s what Strava says about the feature: 

“Strava’s Performance Prediction feature is powered by an ML model that leverages over 100 athlete data attributes, including all-time run history and top performances. Unlike other race predictors that rely on theoretical inputs like estimated VO2 max, Strava only uses real activity data to predict race results. The system also leverages the performances of athletes with similar training histories, so estimated times are realistic and based on what has been achieved by other users with similar capabilities.”

In other words, the app is doing some AI magic: looking at everybody else’s training and race times, considering yours, and guessing how you might measure up to the aggregate. I asked whether Strava had done any testing to see how well the data compares to real-life race results, but so far have not received an answer. (I’ll update if I hear back.) 

Certainly the predicted results I'm getting are pretty different from what I’m seeing elsewhere. I’ve been logging all my runs with Garmin and Strava for several months now, and here’s how their race time predictions compare: 

• 5K (3.1 miles): Strava says I can run this race in 29:22 (up 21 seconds in the last 30 days); Garmin says 26:02 (down 50 seconds in the past 4 weeks)

• 10K (6.2 miles): Strava predicts 1:01:50 (up 5 seconds); Garmin says 55:31 (down about 90 seconds)

• Half marathon (13.1 miles): Strava says 2:24:57 (up 2:43); Garmin says 2:07:09 (down about three minutes) 

• Marathon (26.2 miles): Strava says 5:04:04 (up 1:50); Garmin says 4:45:58 (down 7:44)

I’m not surprised that they differ, but it’s strange that Strava thinks I’m getting slower, where Garmin thinks I’m getting faster.

I don’t have any super recent race times to compare these to, but last fall I ran a 5K in 26:04. The morning of the race, Garmin predicted I’d run it in 25:50, so the Garmin was only 14 seconds too optimistic. According to that same Garmin algorithm, I’m close to that same fitness level right now, so I’d bet money that if I ran a 5K this weekend, I’d be in the low 26 minute range. 

I’m currently working through a 5K plan with the Runna app, and it predicts a 26:15 finish time at my current fitness. (For the other distances: 55:50, 2:08:22, 4:45:33). On a gut-check basis, this one sounds the most correct to me, at least for the 5K. 

I don't trust Strava's predictions

Strava’s prediction of 29:22 sounds way too slow to me. In fact, according to data I can look up in my Strava account, this past weekend I ran 5 kilometers in 30:03 (just a smidge slower than its 5K race prediction) during a five-mile run. That wasn’t a race, and I was clearly pacing myself for a five-mile effort rather than a three-mile one. 

Based on my 5K time of 26:04 (again, an older time, but it’s probably close to my true fitness level), the simple calculator at vdoto2.com thinks I could do a 10K in 54:10, a half in 2:00:23, and a full marathon in 4:07:43. Calculators tend to be a little too optimistic, especially if you put in a shorter race time and ask it to extrapolate out to long distances. So I wouldn’t expect to run a 4:07 marathon anytime soon. 

Judging from forums like the r/Strava subreddit, the jury is still out on accuracy. Here’s somebody who ran a 10K in 56:34, but the app predicts 57:58—a number they just beat by almost a minute and a half. On the other hand, several runners in this thread say that their Strava predictions seem pretty accurate. Only running a race will tell you for sure. 

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