Prep for Your Drug Test with Our Online THC Calculator

Find out if you're positive
MarijuanaBreak Staff MarijuanaBreak Staff / Updated on September 3, 2018

Online THC Calculator

Welcome to the 21st century, ladies and gentlemen. In addition to being able to smoke weed out of futuristic James Bond-looking devices, we now live in an age where we can grow pot for specific genetic traits, drink cannabis-infused water for health benefits, and (for better or worse), jam pack a dime-sized piece of concentrated hash oil with up to 99% THC extract.

And now, believe it or not, we can even use a THC drug test calculator to estimate the amount of active weed metabolites in our system prior to taking a marijuana drug screening.

Try our Online THC Calculator and See How you Score:


That’s right – if you’ve ever wondered how long does marijuana stay in your system, well you can use a  calculator like devices which can be used to record specific personal information (age, weight, height, etc) and give you an estimation of how much traceable THC is likely to be in your body’s cell and tissue systems (including urine, blood, hair and saliva) at any given moment.

In this discussion, we go over what exactly marijuana drug tests are, how they work, and how you might be able to use a THC drug test calculator (try ours out down below!) to increase the likelihood of passing your next randomized drug screening.

Enjoy, pot lovers everywhere — and welcome to the future!

weed calculator

What is a THC Drug Test?

If you’ve ever interviewed for a job before, you’re likely already somewhat familiar with the horribly awkward (and inconvenient) process of a THC test. You know how it goes – the drug test lady hands you a sterilized plastic cup, stands three feet away from you (in a dead-silent bathroom), and waits impatiently while you try and “fill ‘er up.”

But did you know that the majority of these THC tests don’t actually test for THC itself? Rather, most of them are actually designed to screen for the presence of THC-COOH, which is a metabolic byproduct of THC that exists in our bodies after the active compound has been broken down by the liver.

You might actually think of smoking weed as a “three-step THC process”:

  1. In the first step, the THC in the raw marijuana flower actually exists as THC-A, which is a non-psychoactive acidic version of the active compound. As soon as we fire up the joint (or bowl, or vaporizer, etc), the heat causes the THC-A to decarboxylate into THC, which of course is the active compound that accounts for our beloved marijuana high.
  2. The second step is the actual process of inhalation (and absorption) into the bloodstream. As soon as the THC-A combusts, it immediately “turns into” THC, at which point we inhale it into our lungs. Once in our lungs, it can absorb into the bloodstream and travel to every nook and cranny of the body to “work its magic.”
  3. The third step is the metabolic process that breaks THC down into THC-COOH, which like we said is the compound that’s actually screened for during a marijuana drug test. Once broken down by the liver into THC-COOH, the metabolite will “travel” to various parts of the body (typically hair cells and fat deposits), where it can stay for days, weeks, or even months.

thc calculator

Of course, this is where the THC test comes in. Depending on what type of screening you’re having, THC tests can scan for metabolites in the urine, skin, hair, nails, blood, or even saliva. Generally speaking THC-COOH is detectable in the hair for the longest period of time (sometimes as much as 90 days), while it is detectable in the blood and saliva for the shortest amount of time (between 1 and 7 days). Depending on your body size and how often you smoke weed (and also on the THC dosage/potency of the strain you’re smoking), urine tests can detect THC metabolites for up to 80 days, though the common time frame is between 10 and 30 days.

[Check out this article for a much more in-depth look at THC detox and dosage and the amount of time metabolites are detectable in your body].

What is a THC Calculator?


A THC calculator is exactly what it sounds like it is: an online calculator where you punch in some numbers (and other data), and it spits out a “guesstimated” answer of how long THC is likely to stay in your system for.

Technically speaking a THC calculator is actually a drug half life calculator, as it estimates the amount of time it will take for THC metabolites in your system to be broken down into smaller, “non-traceable” compounds.

One important thing to keep in mind though, is that this is NOT an exact science – here at MarijuanaBreak we have spent a considerable amount of time putting together and programming our very own THC calculator (check it out down below), but we are certainly not able to claim that it is 100% accurate.

In other words, if you use our calculator and it estimates that THC will be in your system for 17-24 days, yet you fail a drug test after say, 28 days, don’t come back and blame us!! At the end of the day, the calculator is designed for estimation purposes only.

How Can a Marijuana Calculator Help You Prepare for an Important Drug Test?

That being said, however, using a drug half life calculator – even for simple estimation purposes – can no doubt help you figure out your best plan of attack for passing an upcoming THC test.

There are a wealth of very specific (and fairly efficient) THC detox kits and drinks out there on the market, but if you don’t have a general idea of how long THC might be in your system for, you won’t have any idea of which one to buy, or how to go about using the one that you do buy.

Moreover, if you get the wrong detox supplements (i.e. if you only get a 10-day program even though THC will probably be in your system for 28+ days), then you’ll significantly reduce the chances of passing your test, in addition to wasting some serious cash on an expensive kit. With that in mind, a THC calculator can seriously be a great tool in terms of helping you plan for – and pass – and upcoming drug test.

What do the Drug Test Calculator Results Mean?

Again, it’s important to understand that the results of the weed calculator should not be taken as a 100%, set-in-stone truth. Rather, the numbers given to you should simply be used to estimate and help plan what kind of a detox program you need to be on in order to ensure the best possible chance of passing your THC test.

Let’s use a specific example to help explain how to go about using the calculator’s results.

drug test calculator

Here is the basic information that you’ll have to put in in order to get the most accurate data for your individual circumstances:

  • First, you’ll need to select whether you want to use imperial or metric units (inches vs. centimeters, pounds vs. kilograms)
  • Then you’ll need to select whether you are male or female
  • Then put in your weight ( either lbs or kg, depending on the units you selected) followed by:
  • Your age
  • Your height (either inches or centimeters)
  • How often you use cannabis (provide your best estimation)
  • What your medical condition is that you’ve been using marijuana for (if you don’t use weed to treat a specific medical condition, just select “recreational use”)

Once you’ve entered in all of the requisite information, you’ll simply click “calculate” and the marijuana calculator will crunch some numbers to give you an accurate estimation of how long you can expect THC to be in your system for!

How to Use a Weed Calculator for Maximum Personal Benefit

Most people use the THC calculator to help determine what kind of a detox kit they’ll need to get to help them pass an upcoming marijuana drug test.

Or, if you are an a situation where your employer is letting you select your own dates to take the test (or if you have to supply a drug test on your own through a third-party company), you can use the THC calculator to help determine when would be the most appropriate timeframe to have the urinalysis (or hair/blood/saliva screening) done.

Moreover, you could potentially use the results of the weed calculator to help you save a lot of money on high-end detox kits. Some of the best detox programs out there can cost upwards of $200 (these are usually for long-term “permanent cleanse” programs that take a minimum of 14+ days), but if the calculator estimates that THC will likely only be in your system for 7-14 days, you could perhaps just get one of the 7 or 10-day kits for substantially less money.

Of course, at the end of the day it is entirely up to you to use your best judgment in terms of what you do with the results of the THC calculator. We’ll say it again that the results should not be taken as 100% accurate, so bear that in mind when making any important decisions regarding drug testing or THC screening.

Check Yourself Using our Drug Detection Calculator

Now comes the FUN PART! You can use our THC drug test calculator below to input your personal information (make sure you enter everything as accurately as possible), after which you can see how long THC metabolites will be expected to stay in your system for!

If you’ve got an upcoming drug test for marijuana, though, we always advise to plan for the maximum amount of detox/abstinence time possible. In other words, if the calculator estimates that THC will be in your system for 7-10 days, yet you know you don’t have to take the marijuana test for 14 days, then go ahead and wait that entire 14-day period (if possible) so you can be on the safe side with regard to passing the test.

Will I Pass My Drug Test? Calculators Don’t Lie… But They Also Don’t Guarantee Anything!

To close, we’ll go ahead and reiterate the fact that this THC detox calculator SHOULD NOT be used as a guarantee that you’ll pass an upcoming marijuana drug test!

It should probably go without saying that if you’re trying to determine how much weed is in your system, a calculator is not the surest thing in the world to provide the most accurate results. Even experts in the field who do this type of stuff on a daily basis claim that it is extremely difficult to gauge exactly how long THC will stay in any one person’s system for, as there are just so many variables to take into consideration (age, weight, frequency of use, diet, exercise routine, etc).

At the end of the day, the most foolproof way to pass a marijuana drug test is to simply abstain from smoking weed for as long as possible! We know that’s probably not what you wanted to hear, but let’s face it – sometimes you just gotta suck it up and do what you gotta do to make things happen.

Of course, though, if you’re in an absolute jam and a THC test has snuck up on you out of the clear blue, you can always resort to a fast-acting same day detox cleanse to drastically enhance the chances that you’ll pass the test – even if you smoked a ton of weed the day before!

marijuana calculator

Want to know how long THC can stay in your system? Try out our Online THC Calculator at the top of the page.

  1. Chris Py
    Tested for weed? Screwed

    The most important part for urine testers is how they test for the chemical that comes from fat releasing the thc compound that is stored. This is why you can hear stories of people passing a urine test an hour after smoking blunts(after being clean). It hadn’t been processed into the fat yet to show in urine(or hair). They would have failed blood/saliva.

    I passed a urine test 48 hours after smoking for a week(week off before that, months on before that), by eating a lot of fatty food and drinking a few glasses of water before it. I am pretty thin so imagine there wasn’t much room for thc to be stored. Believe I was over 25ng, but under the 50ng. Don’t try this, but it may help with no other choices.

    Women are naturally fattier than men(bewbs)
    Fattier people will have a harder time and can test+ months after quitting
    First pees of the day will have a higher concentration.. flush that out
    Being active before testing is probably a bad idea as your body will be breaking down more fat
    Being lazy and building fat might reduce the amount of chemicals released
    Limits used to be 50ng, and then upped to 100ng because of false positives, but reduced to 50ng again. This was because lots of fails could pass by drinking a lot of water to dilute their urine. Dilute your urine!

    Bottom line is you are screwed most likely if you get surprised tested for weed. A hit of decent stuff can make you fail a week or two later. Weed is the easiest way to fail a test. Get your laws changed and put pressure on DC to drop the federal demonization of it.

  2. Jason Friel
    Need help

    My partner is still testing positive after giving up smoking weed 80 days ago, she’s been diagnosed with a bowel disease (colitis). She had 90ng in her system could her illness be slowing the process

  3. David
    Help please

    I used to smoke most evenings and weekends but haven’t had any in 11 days. They do random urine drug tests at work. Do you think I’ll be clean now? I drink a lot of water and I’m pretty active. Just wondered if anyone can advise if you think my system should be clear?

  4. Cori
    Any idea??

    I vacationed in California April 17th to the 23rd. I had some edibles maybe 5 of the days I was there. I have to take a drug test this week. Do you think I will pass??

  5. Khylind
    Proof this is roughly legit- wow

    Impressed on accuracy!
    I’m a 18 old female weighing 115 lbs and at a height of 5’4 (average; 64”)
    Before when I was put on probation for marijuana And paraphernalia charges. I had however long until papers went through to get clean and talk/play the system, in less then 30 days with heavy chronic use i dropped clean.
    Because of my personal experience and my found religion, I still believe any mind altering substance fogs your brain from potential-except marijuana (but even marijuana can do this)
    if you’ve ever been a true pothead you’ll understand how marijuana is beautiful to all senses- and if you have a spiritually inclined soul- One blunt after a followed detox before bed is a phychedelic trip through the f*cking universe!
    After My liver detoxes the TCH (without detox) takes maximum 72 hours. Thats after smoking a potent wood and a nice tight g blunt to myself before bed.

    – hope this helped my fellow hippies who just wanna get out of court just for smoking a damn blunt😂😂

  6. Michael
    Need immediate help

    Last time I smoked was April 26th and I take a drug test tomorrow, but I’ve only smoked 4 times in April so you think I’ll pass

    1. Bryan
      Good luck


  7. Ana
    Help plz 🙂

    I smoked daily for 5 months straight and have been clean for 7 days exactly.I am on a Nutracleanse Ultra 10 day detox for daily smokers.I had bought it when I was supposed to get urine drug tested next month but was able to move it back until July 12th. I was told to avoid exercising because it releases the THC but I’m not sure if I would consider two months short term(which is why they tell me don’t exercise).With the detox and additional time,is it likely that I will be clean in time.I understand a home drug test is the only way to be sure but I was just interested in having a professional opinion. FYI when I take the test it will be about 74 days of me not hitting my dab pen.I am 5’3,female,155 pounds

  8. Dave Christensen
    I took nothin. And passed

    I had a drug test but I also take Andro gel which elevated my liver enzymes making me urinate more I smoked every day maybe three bong hits at night a small bowl I stopped and in nine days I pass the test with no problem All I did was drink vitamin water and didn’t eat fat foods I’m 58 my body weight is 167 and I have a very fast

  9. Brian
    Please help

    I took two pulls and found out later that i have a drug test tomorrow. I rarely smoke, i am very skinny and weigh about 120. What should i do ?

  10. Wiz Khalifa
    Please help

    I smoked about 12 days ago and have a drug test on May 23 It says it takes 22-30 days will I be safe?

    1. George @Marijuanabreak

      If you are taking a urine test you should be OK.

  11. Joe Ball
    How much THC

    One might feel that all these online calculators and things like these are not much accurate. But still these provide rough estimates and are good to use. It is like something is better than nothing, and you get at least some idea about how much THC you are exposed to.

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