Stryd is very accurate out of the box for pace & distance tracking and does not require calibration to receive meaningful and useful pace & distance data.
In most cases, Stryd users will be best served using Stryd without a calibration factor!
This article is meant to educate you on how to properly evaluate the pace/distance data from Stryd to increase your confidence in your Stryd pod.
If you are interested in verifying Stryd's accuracy and potentially fine-tuning Stryd's accuracy with a calibration factor, this article will explain the following:
How to Properly Test Stryd's Pace & Distance Accuracy with a Controlled Test on a Measured Track
Note: In most circumstances, it is difficult to test with the precision necessary to confidently improve upon Stryd's accuracy.
The testing procedure described here is detailed and requires a high attention to detail.
If you are not comfortable or do not have access to the tools required to complete the test, you may want to move on to the final section called: Should I use a calibration factor for Stryd's pace/distance?
Measure the distance of the track
If you are certain that the track you use is certified competition distance, then this step is not necessary.
We recommend measuring on the inside line of lane 2 (depending on lane width, the distance for a certified track should be about 405.8 meters).
It is nearly impossible to run exactly 400 meters on the track, as the centerline of the track is 20 cm from the inside line of lane one and is almost impossible to follow exactly (on rare occasions it will be 30 centimeters away if the curb is raised).
You must use a reliable distance wheel and a steel ruler. Do not use a GPS device. We have found tracks that are 1% off the reported 400-meter distance. We have also used certified courses that were marked poorly or did not adhere to standards so it is important that you know the exact distance you ran with your trusted measurement.
Cheap measuring wheels cannot be used as they are inaccurate. You need to purchase a premium wheel. An example of an inaccurate measuring wheel: Keson RR310, and an accurate one: Keson mp401 metal frame measuring wheel. Our testing showed that the inaccurate wheel can be off by multiple meters per lap.
Unwind your steel ruler (i.e. 10 meters or 30 feet) and verify the accuracy of your distance wheel along the steel ruler. Determine the accuracy of the measuring wheel (cheap measuring wheels may pass this test but will still be inaccurate in the turns).
Measure the distance of the inside lane of line 2.
Make note of the exact distance of the track/path. Be sure to mark the start and finish lines.
An article about track geometry: http://datagenetics.com/blog/may12015/index.html
You can select a different line if you prefer. Below is a table to show the distances of the various lines of a track:
Inside Line of Lane | Measured Distance (m) |
1 | 398.12 |
2 | 405.78 |
3 | 413.45 |
4 | 421.11 |
5 | 428.78 |
6 | 436.44 |
7 | 444.11 |
8 | 451.77 |
Step 1: Ensure Stryd is properly placed & firmly attached to the shoe
You must make sure Stryd is attached to the shoe properly. Slide Stryd’s clip under multiple rows of laces to ensure a snug fit and Stryd must be centered on your foot. If you are running counterclockwise on the track, make sure Stryd is on your left foot (or right foot if you are running clockwise).
If you are concerned about accuracy during a race, do the track test with shoes you typically use during an event
Step 2: Ensure your watch is recording pace/distance from Stryd by pairing Stryd as a foot pod and properly configuring the connection
Connect Stryd to your watch (you can use any watch that supports foot pods). Most watches allow you to force the foot pod to be used for speed and distance (and not use the GPS). (Find proper pairing instructions for your Garmin watch here>>)
There will be a calibration option. Set calibration to manual. Set the calibration factor to 1.000 (on COROS, Apple, Polar, and Suunto), or 100 (on Garmin).
Turn GPS off
Step 3: Locate the starting line and start the test with a controlled starting procedure
Do a quick 60-second jog before you start the effort to ensure Stryd is awake. You should start your run within two minutes after the quick jog.
Put your Stryd foot on the start line.
Follow the painted line around the track, or follow the track as you measured it in step 1 (your Stryd should always be in the middle of the line).
Step 4: Run on the marked path
It is important to treat this test like a completely separate run. Do not save your warmup in the same run file as this test!
Start with your Stryd foot on the starting line and wait for 10 seconds
We recommend doing an 8-lap (3248 m) run (do not walk)
It is recommended to run at your race power target for the test. So if you are training for a Marathon, run at Marathon power/pace.
Be sure to stay on your marked path. Every foot strike must land on the marked path. If this does not happen, your testing result will not be relevant because we will no longer know the exact distance that you ran.
No need to hit the lap button each lap as it is not possible to always hit the lap button at the correct point. Just focus on the pace and running with your foot on the line.
Step 5: End the run with a controlled stopping procedure
Stop immediately on the line. Be sure to step on the finish line with the foot that has Stryd on it and do not take a step further. This is a must. Wait 10 seconds before stopping the watch after standing still at the finish line.
Step 6: Sync the watch to analyze your results & Sync the foot pod to verify the pace/distance values were recorded by Stryd
Sync the watch with your online platform (i.e. Garmin Connect). Check the exact distance as measured by the watch for your eight laps.
Optionally: sync the foot pod with the Stryd mobile app as well, so you can compare the distance measured by the watch with data straight from Stryd (note that Stryd does not record laps). Note that you should set up a secondary Stryd account to avoid data duplicates.
If you want to update the calibration, see fine-tuning the accuracy of my Stryd for Garmin & COROS, Apple Watch, and Mobile App below.
How to fine-tune Stryd's accuracy with a calibration factor
This section will describe how to determine the appropriate calibration factor to apply to the pace/distance from Stryd if you would like to fine-tune Stryd's accuracy.
Garmin & COROS Watches
Calibration Factor = (Actual distance you ran / Distance Stryd reported) x 100
For example, if you ran 10000 meters and Stryd reported 99800 meters, the calibration factor would be 100.2
On Garmin watches, you can set the calibration factor on the watch by going into Settings --> Sensors and Accessories --> FP - (number). Scroll down to make sure the Garmin always gets speed and distance from Stryd. Scroll down more to the Calibration factor. Enter the number calculated above.
On Coros watches go to System > Accessories > Added List > Stryd. Check Distance Setting to make sure Coros is getting pace and distance from Stryd. Select Calibration Factor to enter your calculated calibration factor.
Stryd Mobile App & Apple Watch
Calibration Factor = (Actual distance you ran / Distance Stryd reported)
For example, if you ran 10000 meters and Stryd reported 99800 meters, the calibration factor would be 1.002
On Apple Watch, you can set the calibration factor on the watch by opening the Stryd Apple Watch App > scrolling down and selecting ‘Settings’ -> scroll down and selecting ‘Calibration’.
On the Stryd Mobile App, you can set the calibration factor on the phone by doing the following: Stryd Mobile App > Settings > Live Run Settings > Calibration Factor
How does the calibration factor work?
The calibration factor only scales the pace/distance value recorded by the watch or phone.
Power and Stryd's other metrics will not be impacted.
If you would like to see the pace/distance Stryd reported without the calibration factor, you can always get data directly from Stryd by completing an offline sync >
Comparing Stryd's pace/distance against race results, track results, and GPS results
This section will explain some of the common pitfalls to be aware of when making comparisons of data from Stryd against race, track, and GPS results.
You want to be aware of these differences so you can appropriately and accurately attribute the differences, rather than attribute the full difference to error due to an issue with Stryd, a race, the track, or your GPS.
Common causes for the track's distance to differ from your expectations
Incorrect or misleading markers on the track that caused you to run shorter or further than you intended to
The track was marked correctly, but the distance of the track differed from the advertised distance of the track
Common causes for the race's distance to differ from your expectations
Incorrect or misleading markers on the course that caused you to run shorter or further than you intended to
The race was marked correctly, but the distance of the course differed from the advertised distance of the course
Common causes for your GPS watch's distance to be difference from your expectations
Satellite Signal Obstruction: Buildings, trees, and other tall structures can block or reflect GPS signals, causing inaccuracies
Signal Multipath: This occurs when GPS signals bounce off surfaces such as buildings or large bodies of water before reaching the watch, leading to erroneous measurements of pace and distance
Weather Conditions: Severe weather conditions can interfere with GPS signal transmission
Satellite Availability: The number of visible satellites and their positions relative to the watch can affect accuracy
Wrist Movement: Excessive wrist movement, other than the natural motion while running, can sometimes cause the watch to record inaccurate data
Start-Up Time: If a runner starts their activity immediately after turning on the watch, it may not have had sufficient time to acquire a stable GPS signal, leading to initial inaccuracies
Firmware or Software Issues: Bugs or glitches in the watch's operating system or the algorithms used to calculate pace and distance can impact accuracy
Switchback or Winding Paths: GPS watches may not capture every turn accurately, especially on trails or routes with frequent sharp turns, leading to underestimation of the actual distance covered
Tunnels and Covered Areas: Running through tunnels or areas where the GPS signal is completely lost will result in gaps in the data, affecting pace and distance calculations
Common causes for Stryd's distance to differ from your expectations & how to troubleshoot these differences
An uncontrolled starting or stopping procedure at the start or end of the race can cause you to capture more or less data than you intended to with Stryd which can lead to a discrepancy.
Ensure you have not recorded more or less data than you intended to by analyzing the activity in detail.
You ran a different route than you intended to
You might feel sure you ran the same route today as you have previously had and are concerned by a notable difference in distance reporting by Stryd. Check and recheck the GPS map of the two routes with meticulous comparison. It is common that subtle yet significant route differences exist, such as turning a block earlier one day than the other or adding an extra loop somewhere.
Stryd was improperly connected to the watch
Be sure your watch is taking pace/distance from Stryd by verifying the sensor connection in the watch's settings.
Auto-calibration was enabled or an incorrect calibration factor was applied to Stryd
Be sure to disable auto-calibration and reset the calibration factor back to the standard, default value to ensure you are not adversely altering the pace/distance from Stryd
Stryd became disconnected from the watch midway through your run or disconnected for a sub-section of your run
Stryd was improperly positioned or placed on the shoe
Note: In general, we do not recommend using GPS, race results, or uncontrolled testing results from the track to test or verify Stryd's accuracy.
If you are confident in your test results, you can use this data to fine-tune Stryd's accuracy but you should keep in mind that it is practically impossible to diagnose and quantify the source(s) of inaccuracy in these scenarios.
You may incorrectly attribute error to Stryd and unintentionally decrease Stryd's accuracy by applying a calibration factor.
Should I use a calibration factor for pace/distance?
As mentioned at the beginning of the article, Stryd is very accurate out of the box for pace & distance tracking and does not require calibration to receive meaningful and useful pace & distance data.
We see that the large majority of Stryd users do not use a calibration factor for pace/distance. Stryd has also been shown to be highly accurate without a calibration factor by third-party reviewers, such as fellrnr.
Unless you have a high degree of confidence in your testing method or you have completed the controlled testing method described in this article, we do not recommend using a calibration factor.
Remember: The primary benefit of using Stryd is the ability to track your running power output, which enables you to train according to a power-duration paradigm rather than a pace-distance paradigm!
Your available training time with Stryd is best served keeping your Critical Power up-to-date, executing structured workouts, and trending your Stryd metrics rather than verifying Stryd's pace/distance accuracy.
Elevation Calibration
Stryd has a barometer, but no GPS. The baseline elevation of your Stryd can be off due to variances in the manufacturing of the barometer, and more than a few hundred feet is not unexpected. The relative elevation is very accurate (within 1 meter), more accurate than GPS (but it will always be off by the baseline level). If you repeat the same run, the absolute elevation may be different as the barometric pressure varies from day to day.