If you smoke one joint how long would it take to come out your system?

The time it takes for your body to rid itself of all THC is dependent on many factors. These include (but are not limited to) your metabolism, your BMI, your consumption of marijuana and your diet.

Generally speaking, if you are a non-smoker and you smoke off a joint in a group setting (we'll say 3 to 5 people) and that's all you smoke, you could probably pass a urine test within 24 hours. This assumes that because you're a non-smoker, you don't take as deep of hits as experienced smokers do. This also assumes that the marijuana you are smoking is "street-grade" marijuana (that is to say, quickly cultivated and mass-produced...low-quality). This ALSO assumes that you follow a specific quick-detox plan (such as niacin overload or detox drinks available at many corner stores and over the internet).

However, non-smokers have tested positive for marijuana days after going to a concert where second-hand marijuana smoke inhalation has occurred. On the other hand, some very consistent smokers have been able to pass drug tests using detox methods.

Long story short, there is no definitive answer to your question, but if you are a non-smoker who had a night of indiscretion and are facing a drug test, I wouldn't worry about it.