antpool has 16.7% of the network with 550peta

works out as about 25peta if you want a good chance of 1 block a day

although luck plays a hand in it and having more hash increases the chances.
but without getting too detailed in all the if's and buts/ luck/chance/competition... if you stick to say 25peta

it works out as about 1800-2000 bitmain s9 asics(13.5th).

.. based on very simplified quick maths. as there's no point trying to do accurate maths because there is no 'guarantee'.
like i said its based on averages, luck and chance.