This article describes how to upload historical activity data or individual activities from Garmin Connect to Strava. If you'd like to learn how to connect your Strava and Garmin Connect accounts for automatic syncing please see our Knowledge Base article on Garmin Sync.
Transferring an individual activity file from Garmin Connect to Strava:
If you have an activity saved on Garmin Connect - you can easily move your ride history to Strava.
1 Login to Garmin Connect (http://connect.garmin.com)
2 Hit the "Activities" link to give you a list of all your uploads
3 Click on each ride (tip: open each in a new tab)
4 Underneath the map, click on the link that says "Export"
5 Choose "TCX"
That will save the ride file to your computer.
Now you may upload your files one at a time by clicking on "Upload Activity" and selecting "upload a file from your computer" (or just click here http://app.strava.com/upload/select)
Bulk Import of activity files to Strava:
From the Strava upload page, you can select up to 25 files at a time for upload after selecting "upload a file from your computer."
Other tools for transferring Garmin Connect data to Strava:
To export data from Garmin Connect in bulk, you can try this 3rd party tool.