I have this posted in my guide as of today, but since it seems to be a relevant time in this thread, I'll throw it up here too.
Multiply the size and time by the same factor to figure it out for your specific game. Remember the SD speeds are a minimum and the load times are a maximum.
Class 2 has a min speed of 2 MB/s. 500MB game = max load time 4 mins 10 seconds.
Class 4 has a min speed of 4 MB/s. 500MB game = max load time 2 mins 5 seconds.
Class 6 has a min speed of 6 MB/s. 500MB game = max load time 1 min 23 seconds.
Class 10 has a min speed of 10 MB/s. 500MB game = max load time 50 seconds.
UHS 1 (U1) has a min speed of 10 MB/s. 500MB game = max load time 50 seconds.
UHS 3 (U3) has a min speed of 30 MB/s. 500MB game = max load time 17 seconds.
Multiply the size and time by the same factor to figure it out for your specific game. Remember the SD speeds are a minimum and the load times are a maximum.
Class 2 has a min speed of 2 MB/s. 500MB game = max load time 4 mins 10 seconds.