So it is pretty hard to guess exactly how tall a plant will be when it is done flowering due to all the variables. The number 1 variable in plant height is how long you veg for. If you veg for longer the plant will be taller and if you veg for less time the plant will be shorter. In general the plants will increase in size by anywhere from 1.5x to 3x their height before the flip. pure indicas or indica heavy hybrids will usually be around the 1.5x-2x mark. I've experienced a pure indica that only grew 6 inches after the flip and another one that grew 16 inches. Different strains but both were about the same size when I flipped. So I would consider that when deciding when to flip to flowering.
+1 strain
2 strains
