Edible dosage calculator

The formula

total mg THC = grams × 1000 × (THCA % × 0.877 + THC %) × efficiency
mg per unit = total ÷ units of infusion
mg per portion = mg per unit × units in the recipe ÷ portions

The assumptions, and where each number comes from

• Your label is right. The calculation starts from the THCA and THC percentages printed on the product. Flower from unlicensed sources has no reliable figure; if you do not know the percentage, you do not know the dose.
• 0.877. Heat converts THCA to THC and releases carbon dioxide. The molar mass of THCA is about 358.5 g/mol and of THC about 314.5 g/mol (PubChem), so 1 g of THCA yields at most 0.877 g of THC. State testing rules and Leafly's cannabutter calculator use the same factor (Leafly shows it as 87.7%).
• Full decarboxylation. The calculator assumes every milligram of THCA converted. At 115–120 °C for 30–40 minutes conversion is high but not necessarily complete, and longer or hotter heating degrades THC to CBN (Wang et al., 2016). See the decarboxylation guide.
• Transfer efficiency. At 100% the result is a theoretical maximum: all the THC ends up in the butter, oil or alcohol and none stays in the strained plant material or the pan. Real home infusions transfer less, and published laboratory analyses of homemade edibles find wide variation, mostly below the calculated figure (Leafly, "Dosing homemade cannabis edibles"). No reliable single efficiency number exists for home kitchens, which is why the field defaults to 100% and you can lower it to see the effect; the safer habit is to leave it at 100% and treat the result as a ceiling.
• Even distribution. The per-portion figure assumes the infusion is spread evenly through the batch and the batch is cut into equal pieces. The recipes on this site are written to make that true; a dressing that was not shaken or a tray cut by eye breaks the assumption.
• Reference points. 2.5 mg or less is the starting amount in Health Canada's consumer guidance and in Leafly's beginner chart; 10 mg is the standardised serving in Colorado's edible-product rules (1 CCR 212-3). Neither is a medical recommendation; they are the conventions this site's recipes are written around.

Worked example

1 g of flower at 18% THCA in 1 cup (16 tbsp) of butter: 1 × 1000 × (0.18 × 0.877 + 0) × 1.0 = 157.9 mg; ÷ 16 = 9.87 mg per tablespoon. Eight tablespoons in sixteen brownies: 9.87 × 8 ÷ 16 = 4.93 mg per brownie, shown on the recipe page as "about 5 mg".

• PubChem, National Library of Medicine: Dronabinol (THC), CID 16078, pubchem.ncbi.nlm.nih.gov/compound/16078; Tetrahydrocannabinolic acid, CID 98523, pubchem.ncbi.nlm.nih.gov/compound/98523.
• Wang M, et al. Decarboxylation Study of Acidic Cannabinoids. Cannabis and Cannabinoid Research. 2016;1(1):262–271. doi:10.1089/can.2016.0020.
• Leafly, How to make cannabutter (87.7% conversion in its calculator), last updated 2026-05-05, leafly.com/learn/consume/edibles/how-to-make-cannabutter; Edible dosing for beginners, last updated 2026-06-05, leafly.com/learn/consume/edibles/edible-dosing; Dosing homemade cannabis edibles: why it's nearly impossible to calculate, leafly.com/news/science-tech/…. Accessed 2026-11-14.
• Health Canada, What you need to know if you choose to consume cannabis, canada.ca/…/what-you-need-to-know-if-you-choose-to-consume-cannabis.html. Accessed 2026-11-14.
• Colorado Marijuana Rules, 1 CCR 212-3, Rule 4-210 (potency testing: a serving above 10 mg THC fails), via Cornell LII, law.cornell.edu/regulations/colorado/1-CCR-212-3-4-210. Accessed 2026-11-14.