By Luke Sumpter Reviewed by: Gloria Payá

When you start your cannabis-growing adventure, there are some things you should keep in mind. Do you have a proper growing environment set up? Are you able to consistently check in on it? Do you know what you want to do with the plant when it's ready? All these things are important, but perhaps just as important is the question of cannabinoid content.

How much THC and CBD is your plant going to have? Once you figure that out, you might wonder what predictions you can make from there. Even before then, you might be curious about what influences these values in the first place. We'll be working to answer all those questions today.

How Genetics Influence THC And CBD Ratios

During a cannabis plant's genetic development, it synthesises both CBDA and THCA (which become CBD and THC when heated) from the same cannabinoid: CBGA. Whether one, the other, or both appear depends on an enzyme that can take one of two forms, which we'll call A isoform and B isoform, that are encoded by the same gene. Since each plant gets two gene copies, there are only three available options. It'll either get two A isoforms, one A isoform and one B isoform, or two B isoforms. This distribution determines how much CBDA and THCA will be in the plant.

Those with two A isoforms will end up being CBD-dominant with minimal THC levels, such as strains like Solomatic CBD. Strains with one of each will end up with a 1:1 ratio, like Painkiller XL and Dance World. Lastly, plants that get two B isoforms become THC-dominant strains. These include many strains we hear about today, such as Royal Gorilla.

Why Strains Have THC And CBD Limits

Today's plants are packed with more THC than ever before. However, they can only contain so much before they hit an insurmountable peak. This happens because both THC and CBD are derived from the same gene, meaning there are strict limits on the possible ratios of either.

For THC, that limit is around 35% THC by dry weight, with most high-potency strains coming in at 25–30%. The upper limit for CBD, by comparison, is around 20–25%, which you can see in strains like Solomatic CBD, which contains 21% CBD. With strains containing significant amounts of both cannabinoids, the limits are even more nuanced. So, for example, a strain that's 30% THC and 10% CBD is improbable, as is the reverse.

Predicting Strain Effects From THC And CBD Levels

Once you have an idea of how much THC and CBD will be in your plant, you can start making some guesses as to what the effects will be. Most of us know the effects of THC-dominant strains: increased appetite, decreased energy, heightened senses, laughter, etc. If it's CBD-dominant, there won't be any psychoactive effects, and you'll instead enjoy more sub-perceptual effects. Strains containing both THC and CBD will range in psychoactivity, and are desirable to many users as their effects tend to be more balanced than those containing predominantly THC.


Calculating Cannabinoid Percentage

Thanks to recent advancements in the cannabis industry, we now have several methods of verifying THC and CBD percentages. Each of these methods has its strengths, but perhaps the most popular is high-performance liquid chromatography (HPLC). Utilised by over half the industry, this method does not require heating and yields consistently accurate results in comparison to other methods. However, other testing methods have vital applications as well, such as gas chromatography, which can detect volatile hazardous compounds. As such, it’s regularly used in residual solvent screenings.

That being said, the most accessible method, and one that still provides satisfactory results, is thin-layer chromatography (TLC). It usually begins as a glass or plastic sheet containing a thin layer of silica gel, cellulose, or aluminum oxide. A solution containing the cannabis sample is then placed on this "plate", where a solvent is drawn up via capillary action to separate the components of the solution. From there, samples are ready to be analised using specialised TLC test kits. It sounds confusing, but it's actually fairly simple in practice. These kits can be ordered from a variety of sources online.

Another method, supercritical fluid chromatography, utilises CO₂ in its supercritical state, where it demonstrates the efficacy of a liquid and the convenience of a gas. Once all is said and done, the CO₂ is recycled, and potentially hazardous solvents are left out of the picture.

Lastly, if you happen to be in one of our Amsterdam Royal Queen Seeds locations, you can have the potency of your buds tested in our GemmaCert machine for an affordable 8€! It’s non-destructive too, so you don’t even have to worry about losing weed during the test!

How to Calculate the THC and CBD Content in Each Gram of Weed

Most dispensaries, coffeeshops, and seed banks will provide data on their products, letting buyers know how much THC to expect in their flowers based on laboratory figures.

Once you’ve received data from one of the aforementioned outlets, you can use these numbers to throw together a quick equation and figure out how much THC or CBD you’ll be inhaling with each gram.

Let’s say you picked up a gram of your favourite strain while roaming the coffeeshops of Amsterdam. While discussing your options with the budtender, they inform you that this particular strain contains approximately 20% THC.

To get an accurate idea of how much THC you’re about to breathe in, simply fire these simple figures through your head:

  • 1 gram = 1000mg
  • 1 gram of the strain contains 20% THC
  • 20% of 1000mg = 200mg

You can apply the same calculation to CBD figures. The high-CBD strain Solomatic CBD contains 21% CBD and ~1% THC. Therefore, each gram offers ~10mg of THC and 210mg of CBD.

Of course, several variables come into play that dictate the exact amount of THC/CBD you'll be consuming. For example, are you leaving your joint burning in the ashtray as you talk philosophy and botany with your smoking buddy? Regardless, the above equation will give you a general indication of how much THC or CBD you're taking in.

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