For a quadrangle: A=SxS. For Circle's: A=Pi r squared. It may be best to treat the circles circumference as the side of a square. Or you could stagger rows like the stars on the American flag.
Determine the area of your space (X) and the area occupied by a single bucket(Y). Number of buckets = X/Y. Note that the "space" will be smaller than the tent because you'll want room around the edges.
Call me over cautious, I'd undergrow the first time. 4-6 plants. I recently switched from a 150 to 250 and was stunned at the difference. A 1K? I'd want to see what a finished plant looked like before venturing further guesses.
maximum 16 plants (4 x 4) with a 0.25 gap around the edge, (pots no bigger than 30cm square, wilma 11ltr pots are 25cm squared)1 plant per foot squared but packed in plants cant grow too tall (so 16 smaller plants maximum 3-3.5ft after flowering stretch)
average 9 plants (3 x 3) gap between pots and around the edge ... giving the plants more space and there for more available height ...4-5ft maximum
minimum 1 plant/tree monster in a dwc system but will have to veg a long time ...4-5months capable but with addiquate height for maximum growing (depending on grow chamber)
personally i would do 16 x 3 fters for a 1k unless its a huge yeilding strain like NL x Big bud then i would do 9 to get the bigger colas ....
bucket size? average buckets as in 30cm square? same still applies ..if the buckets are bigger than 30cm square do 9 sites... if i were you id get a 600 not a 1k light the heat is stupid and if you get a digital 600 the lumen output is pratically the same with =in 5% of the useable lumens