You can easily estimate your Training Stress Score (TSS)® for outdoor rides directly from your Calendar.
To estimate TSS for an activity, simply right-click on the activity in your Calendar and then select "Edit Workout."
If your outside activities contain heart rate data, you can select "Heart-Rate-Based" to use our Heart Rate-Based machine learning system to estimate all activities with Heart Rate. You can control these settings in your account settings here.
Otherwise, you can use RPE to estimate TSS as well.
If you're looking to estimate TSS for running activities you can use RPE.