What total THC includes
Total THC estimates the amount of delta-9 THC available after THCA loses carbon dioxide through decarboxylation. THCA is heavier than THC, so the conversion uses a molecular-weight factor rather than a one-to-one addition.
The common formula is total THC = delta-9 THC + (THCA x 0.877). It is widely used for potency math, but actual consumed THC can be lower because decarboxylation, extraction, cooking, storage, and product homogeneity are not perfect.
- Use lab-reported delta-9 THC as already active THC.
- Multiply THCA by 0.877 before adding it.
- Keep percent, mg/g, and package milligrams separate until converted.
How to calculate
If a flower sample has 18.0 percent THCA and 1.2 percent delta-9 THC, total THC percent = 1.2 + (18.0 x 0.877) = 16.986 percent. Rounded reasonably, that is 17.0 percent total THC. In mg/g terms, 17.0 percent equals 170 mg per gram because 1 percent equals 10 mg/g.
For a recipe using 3.5 g of that flower, theoretical total THC = 170 mg/g x 3.5 g = 595 mg. If the batch is divided into 20 equal servings, the theoretical value is 595 / 20 = 29.75 mg total THC per serving before accounting for process loss.
Serving math for edibles
For infused products, serving potency depends on total active cannabinoids in the whole batch and the number of uniform servings. A 100 mg package cut into 10 equal pieces is 10 mg per piece. A 100 mg oil bottle with 20 mL total volume contains 5 mg/mL, so a 0.5 mL dose contains 2.5 mg.
Manufacturers and home formulators should also account for dilution and yield. If infused butter, oil, or concentrate is not fully transferred into the final recipe, the package calculation based on starting material may overstate actual serving strength.
- Package mg per serving = package total mg / number of servings.
- Liquid mg per mL = package total mg / bottle mL.
- Recipe mg per serving = batch mg / finished serving count.
Who needs this calculation
Processors use total THC and per-serving math to design batches, check label claims, and avoid accidental overages. Retail teams use it to explain why a high-THCA flower may have a high total THC value even when delta-9 THC alone looks low.
Consumers use the same arithmetic to compare products, but potency math is not dosing advice. Individual response varies with tolerance, route of use, food intake, medication interactions, and local legal limits.
Common mistakes
Do not add THCA and delta-9 THC directly without the 0.877 factor. Do not treat percent as milligrams per serving without multiplying by product weight. Also avoid assuming every piece in a batch is identical unless mixing, depositing, and cutting are controlled.
Another mistake is ignoring moisture basis. Flower results may be reported on an as-received or dry-weight basis depending on the lab and regulatory context. Use the basis stated on the certificate of analysis when comparing numbers.
Frequently asked questions
Why is THCA multiplied by 0.877?
THCA loses carbon dioxide when converted to THC, so the resulting THC molecule weighs less. The 0.877 factor adjusts for that molecular-weight change.
Is total THC the same as delta-9 THC?
No. Delta-9 THC is already active THC reported by the lab. Total THC adds the delta-9 THC to the converted potential THC from THCA.
How do I convert THC percent to mg/g?
Multiply the percent by 10. For example, 15 percent THC is 150 mg/g because one gram contains 1,000 mg.
Why can calculated edible potency differ from lab-tested potency?
Extraction efficiency, decarboxylation, cooking loss, incomplete transfer, and uneven mixing can all change the final tested value.