The short answer
THC percent is the share of the product's weight that is THC. One gram of 20% flower holds about 200 mg of THC. The number does not say how strong the product will feel to you. Route, dose, and tolerance decide that.
What the number measures
A lab tests a sample and reports a weight percentage. 25% THC means 250 mg of THC in 1 gram. 10% means 100 mg in 1 gram. Flower labels list total THC. Total THC is THC plus THCA, counted after decarboxylation.
Typical ranges
- Flower: 15% to 25% total THC in state-licensed stores.
- Pre-rolls: 15% to 25%, same as the flower used.
- Vape cartridges: 60% to 90%.
- Concentrates: 60% to 90%.
- Tinctures and oils: 5 mg to 50 mg per mL.
- Edibles: listed in mg per serving, not percent.
THCA turns into THC
Fresh cannabis holds THCA, an acid form. Heat removes a carboxyl group and converts THCA to THC. A vape at 350 F does this. A lighter does this. An oven does this. Edible makers run a decarboxylation step before mixing. Flower eaten raw delivers less THC than the label implies.
A first dose
Inhaled: one or two puffs of flower, then wait 10 minutes.
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Oral: 2.5 mg to 5 mg THC, then wait 2 hours before the next dose.
Colorado sets one edible serving at 10 mg THC and a retail package cap at 100 mg. Health Canada caps a full package at 10 mg THC. A starter dose sits below both limits.
Why two labels differ
A lab sample comes from one part of a batch. THC content varies across a plant, across buds on the same plant, and across a harvest. Labs use different methods and different detection limits. Some studies of dispensary flower found labeled THC did not match measured THC in a portion of samples. Treat the number as an estimate, not a measurement of your batch.
What percent does not tell you
Terpenes, other cannabinoids, harvest date, and cure change the experience. Two samples at 22% can feel different. High percent raises tolerance faster and raises anxiety risk for new users. Cost per milligram of THC compares products better than percent does.