Stryd is designed to be accurate out of the box without calibration for most runners, but there are exceptions. If you ran a marathon (or other race) and found that Stryd did not measure the exact distance, these steps will help avoid future problems.
Check the watch settings and Stryd attachment
Compare Stryd with watch data. This is a complicated step, contact us if you need assistance.
A marathon course is at least 26.2 miles or 42.2 km. The course distance can be longer. Additionally, it is practically impossible to run the shortest line. You likely will run a distance longer than a marathon (up to 0.5 miles is not unexpected).
Stryd will be consistent between shoes if Stryd is in exactly the same position on the foot regardless of shoes. Some runners may experience that Stryd can be inconsistent with the current firmware if Stryd is not in the same spot. An example is the Nike Next% that has lacing that can cause Stryd to move to the side of the foot. If not corrected, Stryd could measure short in those cases (i.e., the distance on your watch exceeds the distance you ran).
Finetuning Stryd pace/distance to avoid future issues:
Head to the track. Run with your race shoes at race pace. The detailed procedure: Distance and Calibration
No access to a track? Use the Garmin Autocalibration feature.
You can use the Stryd measured distance to get an estimate of your calibration factor: 42.2 km / Stryd distance * 100