How is an API call counted?

Tomorrow.io's plans differ in restrictions of API calls, therefore it's important to understand exactly how much data you can get with an API call.

1 endpoint, 1 location = 1 API call
For the data endpoints, one API call gets all time steps of a data type (realtime/forecast/historical) for a specific time period for one location. For example, /realtime returns the requested data fields for a lat/lon right now. And so, a developer building an application would be charged one API call to get this location's numerical data.

Similarly, requesting a single map tile is equivalent of a single location only with that the data format is visual (png image) and the location data spread (or area) is defined by the zoom level. If a developer requests a x,y,z tile the precipitation that is occurring now, they will consume 1 call out of their limit. Therefore, requesting a tile for one location is also a single call. 

Lastly, Tomorrow.io widgets are also counted in the same manner, such that each forecast update is a single API request.