Any where from 8-15 weeks. Most Indica dominant plants take around 10 weeks while Sativas can take up to 18 weeks. There are SO many factors involved that without information regarding the plants genetics and its growing environment, an educated guess is impossible. Get a jewelers loop or a cheap microscope and start looking at the trichomes in about 6 more weeks. When about 40% are cloudy, 40% are amber and 20% are red the plant is ready to harvest.