Depending on the video quality that you use, the data usage will vary. When you are watching a movie with video quality set to Good, Fire TV Stick consumes about 900MB of data/hour. It will consume about 3.5GB data while watching videos in Best quality. 4K videos will consume about 6GB of data/hour.
Fire TV Stick shows data used by apps over the past 30 days (you need to set the billing cycle first). You can even set an alert to stop crossing a specific data limit. However, it cannot control the data usage by apps.
Step 1: Navigate to Settings > Preferences with the help of Fire TV Stick remote.
Step 2: Select the Data Monitoring option and then press the select key to check if the data monitoring is turned on or off. The feature is turned off by default. To turn it on, press the select button again (when Data Monitoring is selected).
Step 3: Scroll down to see the Monthly Top Data Usage option. Select that option and then press the select button on the remote to see the data usage by apps.
To set a billing cycle, please navigate to Settings > Preferences > Data monitoring > Set data alert, and then select the billing cycle start date.