How Long Does It Take for a Joint to Get Out of Your System?
This is the most common question asked by cannabis users. Well, there’s no simple answer to this question, as there are so many variables that dictate how fast or slow a joint can take to get out of your system. However, if you’re a weed user looking for answers before a scheduled drug test, there are two major factors that can make a difference—your physiology (as all people are different) and the amount of THC in a joint.
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How Much THC Is in One Joint?
In most cases, the amount of THC varies from strain to strain, from 5% to upwards of 30%. In our case, let’s take an average level of 15%.
The average weight of a single joint is estimated to be 0.32 grams according to an article published by Christopher Ingraham in The Washington Post. 
Knowing this, we can calculate how much THC is in one average joint. Here’s the math:
0.32 grams = 320 milligrams
15% THC of 320 mg = 0.15 × 320 = 48 mg THC
If you’re smoking half of an average joint, then you consume 12 mg to 14 mg of THC, with about 10 mg to 12 mg going to the sidestream. On the other hand, if you’re smoking an entire joint, then the average amount of THC consumed will range from 19 mg to 23 mg.
Another common joint size from the same article was 0.75 grams according to a survey among marijuana users by High Times based on 3,000 responses. Here’s the amount of THC calculated from this joint size:
0.75 grams = 750 milligrams
15% THC of 750 mg = 0.15 x 750 = 112.5 mg THC
In this case, if you smoke half a joint, you will consume about 27 mg to 32 mg THC. On the other hand, if you smoke an entire joint, you’ll consume between 50 mg and 60 mg THC, with a sidestream loss of about 40–50 mg THC.
Many other variables also determine how much THC is consumed. For instance, lung capacity, how much you inhale, and how long you hold your breath after each puff are some factors that will determine the amount of THC you consume. Another factor is sidestream smoke, where much THC is lost as you await the next puff.
Also important is the change in THC in the joint as you smoke. As the joint burns, more THC condenses toward its end, making the second half of the joint have a slightly higher THC level than the first half.
In the table below, you can see the approximate amount of THC in the joint depending on the THC level in the cannabis strain:
|Pinner (0.32 gr)||16 mg||32 mg||48 mg||64 mg||80 mg||96 mg|
|Joint (0.75 gr)||37.5 mg||75 mg||112.5 mg||150 mg||187.5 mg||225 mg|
How Long Does THC Stay in Your System?
Here’s the science behind it:
According to a study, after smoking about 27 mg of ▵9-THC in a joint, THC-COOH in a smoker’s urine was peaking at 180 ng/mL after 4 hours. 
According to another study, it was discovered that THC half-life goes from 1.4 days in the first days after smoking (without any major differences between frequent and occasional users) to approximately 4 days for occasional users and 7 days for frequent users in later days. 
This means that 27 mg will require about 3 days to get below the recommended 50 ng/mL drug test threshold because after 1.5 days it will be 180/2 = 90 ng/mL, and in the next 1.5 days, it will be 90/2 = 45 ng/mL.
For a confirmation test with a 20 ng/mL cutoff, infrequent users will need almost 5 days to test negative, while frequent users will need up to 7 days.
However, it’s good to keep in mind that these calculations may vary significantly depending on many variables, which include age, body mass, lifestyle, and personal metabolism.
Read more: How Long Does Weed Stay In Your System?
How Long for One Joint to Get Out of Your System?
Here is the math:
In the study above, a weak marijuana strain was used. Let’s take their findings and recalculate the number of days for other strains knowing how much THC is in the joint.
An average pinner with 15% THC has 48 mg of THC, which gives near 320 ng/mL of THC-COOH in the urine after smoking. This concentration will be reduced to 160 ng/mL in 1.5 days, 80 ng/mL in 3 days, and 40 ng/mL in 4.5 days, so you need almost 4 days to pass a drug test after smoking such a joint. Since THC half-life later grows to 4 and 7 days for infrequent and frequent users respectively, you may need from 8 to 11 days to get below 20 ng/mL and pass a confirmation test.
For a joint with 15% and 112.5 mg THC, the calculation will be 750 ng/mL THC-COOH after smoking, 375 ng/mL in 1.5 days, 187.5 ng/mL in 3 days, and almost 94 ng/mL in 4.5 days. With an increasing half-life it will take 8–11 days to get below 50 ng/mL and from 10 days to 2 weeks to get below 20 ng/mL.
Days to pass initial drug test with 50 ng/mL cutoff:
|Pinner (0.32 gr)||Joint (0.75 gr)|
|Casual user||Heavy user||Casual user||Heavy user|
NOTE! The calculations here are estimates, as personal metabolism has a major impact on the time THC needs to get out of your system.
To get THC out of your system completely down to zero, you need almost one month for infrequent users and a few months for heavy smokers.
How to Find the Exact Time?
To find the exact time a joint needs to get out of your system, you need to buy a home drug test to test yourself and control the level of marijuana metabolites in your system. One of the best home tests available is the UTest-O-Meter Multi-Level Home THC Urine Test. Unlike the usual tests, this one checks THC in the urine in 4 different levels, which are 20 ng/mL, 50 ng/mL, 100 ng/mL, and 200 ng/mL. This helps you to better understand how fast your body cleanses itself from traces of weed.
How to Reduce This Time
To speed up THC withdrawal and reduce the time a joint needs to get out of your system, you need to drink a lot of water, urinate frequently, and use marijuana detox kits to cleanse your urine and avoid failing a drug test.
- One of the big questions in marijuana research has been answered. Christopher Ingraham - The Washington Post.
- Chemistry, Metabolism, and Toxicology of Cannabis: Clinical Implications. Priyamvada Sharma PhD, Pratima Murthy, M.M. Srinivas Bharath - NCBI.
- Urinary Excretion of 11-nor-9-Carboxy-AgTetrahydrocannabinol and Cannabinoids in Frequent and Infrequent Drug Users. Anne Smith-Kielland, Bjørn Skuterud, Jørg Mørland - Journal of Analytical Toxicology.