Marijuana Drug Test Calculator. Will You Pass a Drug Test?

The calculator uses information and statistical data from the latest medical, scientific researches and studies to emulate the processes of marijuana metabolism in the body. Read how the calculator works.

It calculates how the THC-COOH concentration in the urine changes over time and when you will be able to pass a drug test.

The results are valid if you consume marijuana in the form of Delta-9 THC or Delta-8 THC or Delta-10 THC.

How to use the calculator

Above, you see the data entry form. You need to enter your physical measurements as well as your smoking habits. Each field plays a role and impacts how long it will take for you to pass a THC drug test.

how to use thc drug test calculator

Here’s the quick synopsis of each variable that is used.

Biometric measurements

Age and Gender

When the THC metabolites get into the blood, the liver removes them from the bloodstream, and then they are excreted through the urine and stool.

As you age, a few factors related to your liver and kidneys begin to decline.

These changes affect how fast THC metabolites can be excreted from the body.

In a nutshell, the THC half-life of an older person is significantly increased; sometimes, it can be as great as a fourfold increase.

The half-life of THC in a healthy adult is between 28 hours to 36 hours.

In an older person, the half-life is prolonged and may take up to 120 hours, depending on the exact age and other factors.

Weight and Body Type

THC is lipophilic, meaning that it binds to fat. From the bloodstream, the THC is distributed into other organs and fat.

Once the THC levels in the blood decrease, the fat cells release the THC that they are holding.

A person with a higher fat percentage will have a prolonged rate of excretion of THC because they have more fat cells holding on to THC and its metabolites.

For fat to be released from the fat cells, it has to be broken down.

It so follows that people with more body fat percentage will store THC for longer and will take a longer time to excrete.

Metabolic Speed and Physical Activity

A study conducted by the University of Sydney in 2006 revealed that exercise prompts the body to go into lipolysis (fat breakdown) and release THC stored in fat cells.

The more regularly you exercise, the faster you can release THC from the fat cells into the bloodstream.

The same for people with a higher metabolism speed. They will have faster lipolysis (fat breakdown), and more THC metabolites will be released into the blood and excreted from the body.

Smoking Habits

Smoking Frequency and Marijuana THC Content

This is required to understand how much THC was consumed. For example, if you smoked just once, you will be able to pass the test within a few days.

Daily smokers will have a lot more THC accumulated in the body, and it will be released into the blood for a long time even after you stop smoking.

Smoking strains with higher THC content will also result in more THC metabolites stored in your body and longer excretion time.

A study conducted in 2007 by the National Institute on Drug Abuse compared a low dose THC with a high dose THC group.

Both groups comprised of non-regular smokers of marijuana. The results revealed that the group given a higher THC dose took twice as much time to eliminate the THC from their bodies.

The amount of weed smoked

Here we assumed that the weight of each smoked joint is 500mg.

Understanding the Drug Test Calculator Results

How to read thc calculator results

  1. Y-axis: the levels of the THC-COOH in the urine. THC-COOH is the metabolite that drug test will detect. When this value is above the drug test cutoff level (50ng/ml) – the drug test will show a positive result.
  2. X-axis: days after you stopped smoking. We assume that the last day you smoked is the 0 day.
  3. The blue line shows how the concentration of THC-COOH changes over time.
  4. The vertical green line indicates the day when the concentration of THC-COOH in the urine will be below the detectable level. On this day, you will be able to pass a drug test. On the image above, the person will be able to pass on day 8.

How calculator works

Our calculator uses the information and statistical data from the latest medical studies and researches on how the body metabolizes the weed.

Here’s how the THC is metabolized by the body and the processes emulated.


When you smoke, the concentration of THC in the blood increases.

THC travels through the body via the bloodstream. Part of the THC is bind by body adipose tissue.

In the liver, THC is metabolized into THC-COOH-glucuronide, which is excreted via urine and stool.

Part of the THC-COOH-glucuronide is metabolized back to the THC-COOH by the bacterial enzymes in the intestines.

This THC-COOH is reabsorbed back into the blood again. This process is called enterohepatic recirculation.

Our calculator uses the studies and data about each of these processes to determine how much THC metabolites will be excreted into the urine.

How accurate the results are

The human body is a very complicated system. There are too many processes going simultaneously, and too many variables consider.

It’s impossible to create a math model describing the body processes precisely.

Using the statistical data from other people will not provide the exact numbers for your situation also. This is because of the lifestyle, and thus the metabolism of any 2 people is different.

The only reliable method to know the exact concentration of THC metabolites in the urine is to measure it in the lab.

Our calculator uses the best-known studies, data, and math methods to calculate the concentrations as precisely as possible.

You can definitely use the data from the calculator to understand how long the detoxification will take.

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