THC percentages tell you how much of a cannabis product’s weight is made up of THC, the compound responsible for the high. A flower labeled at 20% contains roughly 200 milligrams of THC per gram. But that number alone doesn’t tell you as much as you’d think about how strong the experience will be, and the labels themselves are less reliable than most consumers assume.
What the Number Actually Measures
The percentage on a cannabis label represents THC content by weight. If you buy a gram of flower testing at 14%, that gram contains about 140 milligrams of THC. A gram at 25% contains about 250 mg. The math is straightforward: multiply the percentage by 10 to get the milligrams per gram.
Most raw cannabis flower doesn’t contain much active THC, though. The plant produces THCA, an inactive precursor that only converts to THC when heated (by smoking, vaping, or baking). That’s why labels list “Total THC” rather than just THC. The standard formula is: Total THC = (THCA × 0.877) + THC. The 0.877 multiplier accounts for the fact that not all THCA converts during heating, and THCA molecules are slightly heavier than THC molecules. When you see a percentage on flower packaging, it’s almost always this calculated total.
Typical Ranges by Product Type
Dried flower on dispensary shelves generally falls between 15% and 30% total THC. In 2022, the average THC concentration for flower sold in Washington state was 21%. Anything above 25% is considered high potency, and products claiming numbers above 35% are exceptionally rare in nature.
Concentrates are a different category entirely. Products like wax, rosin, shatter, and hash oil generally range from 60% to 90% THC. The average concentrate in Washington state tested at 69% in 2022, though traditional concentrates like hash and kief come in lower. Distillates often sit at the top of that range because they’ve been refined to isolate THC from nearly everything else in the plant.
Edibles are labeled in milligrams rather than percentages, typically in doses of 5 or 10 mg per serving. If you’re used to thinking in percentages from buying flower, the conversion is simple: a single gram of 20% flower contains 200 mg of THC total, which is equivalent to 20 standard 10 mg edible doses.
Why Higher Percentages Don’t Always Mean a Stronger High
This is the part most people searching this topic really need to know. THC percentage is one variable among several that shape your experience, and chasing the highest number on the shelf is a bit like choosing wine solely by alcohol content.
Cannabis contains dozens of terpenes, the aromatic compounds that give each strain its distinct smell. Research published in Scientific Reports found that several terpenes don’t just add flavor. They interact directly with the same receptor systems that THC targets. Terpenes including humulene, linalool, and pinene produced cannabinoid-like effects in animal studies on their own, and when combined with cannabinoid compounds, their effects were additive. In practical terms, a flower at 18% THC with a rich terpene profile can feel more potent or produce a qualitatively different experience than a 25% flower that’s been stripped of its terpene complexity.
How you consume also matters enormously. Smoking a joint wastes a significant portion of THC to combustion and sidestream smoke. A dry herb vaporizer extracts more efficiently at lower temperatures. And your own biology plays a role: your tolerance, body composition, how recently you ate, and your individual receptor density all influence how any given percentage translates into what you actually feel.
Label Accuracy Is Worse Than You Think
Here’s where things get uncomfortable. A large study published in Scientific Reports tested cannabis products from legal dispensaries and found that only 56.7% of flower products were accurately labeled, using a generous accuracy window of plus or minus 15%. A separate investigation of 107 recreational flower products collected at random from dispensaries in California, Oregon, and Colorado found that over 70% fell outside of a 20% accuracy threshold.
The reasons are partly structural. Cannabis prices are heavily driven by THC percentage, which creates a financial incentive for everyone in the supply chain to push numbers higher. The industry term for this is “lab shopping,” where cultivators and dispensaries seek out testing labs known to generate higher results. Labs that consistently report lower (potentially more accurate) numbers risk losing business. Some producers also manipulate which part of the plant gets submitted for testing, since small buds near the top of the plant test higher than larger buds from lower branches.
This means the difference between a product labeled at 22% and one labeled at 28% may be smaller than it appears, or may not exist at all. Treating the number as a rough guide rather than a precise measurement is more realistic.
How to Use THC Percentages Practically
Think of THC percentage as a dosing tool rather than a quality score. If you’re newer to cannabis or have a low tolerance, starting with flower in the 10% to 15% range gives you more room to control your intake. Each puff delivers less THC, making it easier to find a comfortable level without overshooting. Higher-percentage products aren’t inherently better; they’re just more concentrated, meaning each hit carries more.
When comparing two similar products, pay attention to the terpene profile if it’s listed. A flower with 2% or higher total terpene content will generally deliver a more nuanced experience than one with minimal terpene data. Some dispensaries now list the top three terpenes by weight, which gives you a better sense of what to expect than THC percentage alone.
For edibles, the math is more reliable because the THC has already been extracted, measured, and dosed into individual servings. A 10 mg gummy is a 10 mg gummy regardless of what plant it came from. This is one reason many experienced users prefer edibles when consistency matters: the dosing is more precise than eyeballing how much of a 24% joint you’ve smoked.
If you’re converting flower to homemade edibles, remember that you won’t extract 100% of the THC listed on the label. The decarboxylation process (heating THCA to convert it to active THC) and any cooking or infusion steps involve some loss. A reasonable estimate is that you’ll capture 60% to 80% of the total THC listed, depending on your method.