How long does marijuana stay in your system?

This is one of those answers that varies based on usage, body fat, metabolism, etc. In general, if you stop using, drink a lot of water and start exercising to generate sweat, most hardcore stoners that have had to get it out of their system will tell you 30 days.

The professionals will 3 to 90 days, with 90 days being for the hair test. For a urine test, about 30 clean days usually works.