I am an application programmer, a beginner in the GIS domain. I have an image with its ground sample distance parameter. I need to associate the zoom level with GSD. I am using MapBox.
My rule of thumb is to consider that the GSD is approximately 0.3 mm on the screen at maximum magnification. You could go down to 0.1 mm for pixel peeping, but then you lose the global view without a large gain in the details (GSD is often optimistic).
Mapbox ecosystem uses tiles that are in Mercator projection (as Google Maps and other do). The GSD will vary not only with zoom level, but also latitude.
This along with size of your tiles (usually 256x256 px or twice that for "retina" hi-DPI, you can peek your network traffic what you're getting) can let you calculate GSD.