All Fitbit trackers are optimized for walking, running, and general household and lifestyle activities. Note that the Fitbit Surge is an exception. Using the bike exercise on Surge accurately tracks your calories from cycling. Other than the Fitbit Surge, trackers are not as accurate for activities like biking. To use your Surge for a bike ride, see Can I track my bike rides and spin classes with Surge?
For increased accuracy if you're not using Surge, go to http://www.fitbit.com/activities or click the "log activity" icon from your dashboard to manually log activities like cycling. This will ensure that a more accurate estimated calorie burn is included in your daily totals. Our online database of workouts makes it easy to save and access your favorite activities. For detailed information see How do I log or record an activity?