Originally Posted by saveri

The bonus is actually on the distance between the cities in each segment. So if a flight segment is actually 1000 miles in distance, Plats get 1000 miles (100%) Gold 750 miles (75%) etc.
This is then on top of the regular miles based on your fare class which can be as high as 300% in first and 25% in the lowest economy fare class. The bonus is not on the regular Avios based on your fare class.
The easiest way to calculate your bonus miles is via Qcalculator actually. Just input the city pair for your flight segment and choose economy and AA. Economy (HKY) is the distance flown and 100% of mileage for Plats. Golds are economy (LMNV) and 75%. Silver is economy (S) and 50%.
See the attached example on a flight segment from MIA to SFO. The "membership" field changes nothing. Distance is 2585 and the bonus for Plats. 1939 is for Gold