There are around 2,200-22,000 ng in a hit of THC, depending on the grade of Marijuana you are ingesting. Your body only naturally gets rid of 7-11ng a day. Marijuana has been known to show up in urine for some users up to 90 days after their last use. Detection times vary depending on many factors, including drug potency, tolerance, relative health of the test-taker, fluid intake at time of test. method and frequency of marijuana use, body type, metabolism, exercise frequency and many others. These are general guidelines only.

The half-life of TetraHydraCannabinol (THC) concentration ranges between 0.8 to 9.8 days. There is too much human variation to even approximate how long THC will be detected in the urine of an individual. Infrequent users with a fast metabolism will have the shortest detection time. Obviously, frequent users with a slow metabolism will have long detection times.

The only way to reasonably estimate your personal detection time is to consider the highest and lowest extremes (3-30 days) and use your best judgment to form an educated guess. The table below can function as a good guide for you.
Again, detection times vary depending upon the analytical method used, an individual’s drug metabolism, tolerance, health condition, fluid intake and method and frequency of ingestion. These are general guidelines only.

There are extreme variations. For example, if you use marijuana on rare occasions, your urine may be clean of metabolites in less than a week. Additionally, there is a common and strange phenomenon reported with chronic marijuana smokers. While you would expect a chronic user to have longer detection times, this is not necessarily the case. A chronic user with a high tolerance will eliminate drugs quicker than an occasional user. Chronic users have even tested negative after a week-long smoking binge. Lipid tissue also makes a significant difference. Thin users not only have a faster metabolism, but also lack the fat storage for THC metabolites. Additionally, more body fat will cause a lag in excretion patterns and lead to longer detection times.

As you can see, individual detection times for marijuana are extremely diverse and unpredictable.