hi folks
i cant decide which prop size should i use.i was thinking of 12*4.5inch on 810kv 2216 motors for max power on 3s setup 4200mah,25 amp esc,i hope it can handle the heat,and one more choice i have is 11*4.7
i tried googling but not so usefull

I have seen people use 10*5 props .. I think that gives max thrust
I think Don't go beyond 11*5 props.. That would just be extra useless amps drawn..
Best of luck

10*5inch prop is good for 4s setup. but not efficeint for 3s ...i think 11 or 12 inch would be good.

Well you can try 12inch but 11 ones would surely work according to me

@shyam hembram,
10x4.5 for 3s. Over 800gms thrust.
See this review:
http://www.flitetest.com/articles/best-450-size-quad-motor

I have used this motor in my quad ,it can give around 800 gm thrust with 10*4.5 setup,still using this setup with dozens of happy flying and draws current max 11-12 amp
And with 11*4.7 setup extra 50 gm of thrust with 14 amp of current draw and yes no doubt mine get heat.Hope this will helpful

Thanks @Sultan sir and @Iyer sir