Cannabutter Dosage Calculator
"How strong will my cannabutter be?" has an arithmetic answer before it has a laboratory one: flower weight × lab percentage × how completely you decarbed × 0.877. Enter the five numbers your recipe actually used and get the batch total, the milligrams per tablespoon, and what that means per cookie.
240°F / 115°C, 40 minutes - the reference cycle on this site
Total potential active THC in the batch
1,104 mg
7 g × 18% × 99.9% × 0.877
Milligrams per tablespoon
69.0 mg
The 1 cup batch is 16 tablespoons. One tablespoon ≈ 13 five-milligram servings - which is why home batches are eaten by weight, not by appetite.
Per portion (24 cookies)
46.0 mg
The even-division ideal. Cannabutter distributes unevenly as it sets, so stir the melted batch solid before you pour or spoon it out, and keep one batch constant across a recipe.
Ceiling arithmetic, not an assay: the real batch sits somewhere below these numbers - see the dosing chart for what the gaps are and how legal edibles close them.
Standard batches, worked out
Same math, three common batch sizes, 18% flower fully decarbed (the table is computed with the same 99.9% conversion the calculator uses for a 240°F / 40-minute cycle):
| Flower per 1 cup of butter | Batch total (mg) | mg / tbsp (1-cup batch) | mg / tbsp (2-cup batch) |
|---|---|---|---|
| 3.5 g | 552 mg | 34.5 mg | 17.2 mg |
| 7 g | 1,104 mg | 69.0 mg | 34.5 mg |
| 14 g | 2,207 mg | 138.0 mg | 69.0 mg |
Read the table before you shrink the flower amount to "make it weaker": at 14 g a single tablespoon carries more than a legal dispensary package is allowed to hold in a whole serving line. Home batches get dangerous at the tablespoon scale, not the cookie scale.
The 0.877 factor, which is also a regulator's factor
THCA (358.48 g/mol) sheds a carboxyl group as CO2 (44.01) and becomes THC (314.47 g/mol), so every gram of acid yields 0.877 g of neutral - that is the whole derivation, and it is why a lab report of 18% THCA promises at most 15.8% THC. This is not a kitchen convention invented for this page: New York's Part 128 packaging and labeling guidance defines "total THC" as THC + (THCA × 0.877) on every dispensary label in the state, and its adult-use rules cap a serving at 10 mg of total THC and a package at 100 mg - Colorado's Rule 212 sets the same 10 mg single-serving ceiling. The calculator runs your batch through the identical arithmetic the retail market is legally required to use; what retail adds - tested potency and industrial homogenization - is exactly what a home batch does not have.
Dosing a batch you cannot test
- Start where regulators start. New York's consumer guidance for first-time edible users is 2.5 to 5 mg - a fraction of a tablespoon in every row of the table above.
- Judge the dose at the right delay. The RTI Press review of cannabis edibles (Barrus et al., 2016) documents oral onset at 30-90 minutes and a peak at 2-4 hours; nothing that has not arrived in the first hour is a signal to take more.
- The ceiling is a ceiling. Infusion leaves THC in the plant matter, and RTI documents potency variance even in batch-tested commercial edibles. The real number is lower than the calculator's; dose the lower-number assumption.
- Label like it is commercial product. Grams, percentage, date on the jar - and the FDA's 2022 advisory is why it stays out of reach of children, in packaging that looks nothing like the snacks next to it.
Cannabutter dosage questions
How many mg of THC are in a tablespoon of cannabutter?
It depends entirely on the recipe: a tablespoon of a 7-gram-per-cup batch at 18% THCA carries roughly 69 mg of potential THC, while a 3.5-gram-per-cup batch carries about half that. There is no universal number, which is the whole point of running your own grams, percentage, and batch size through the calculator above.
What is the 0.877 in THC math?
The molar-mass ratio between THCA and THC: the carboxyl group weighs 44 of THCA's 358 g/mol and leaves as CO2, so 314.5/358.5 = 0.877. It is not a home-kitchen convention - New York's cannabis labeling rules define total THC as THC + (THCA x 0.877), the same factor this calculator applies.
How much cannabutter is a 5 mg dose?
Divide by strength: in a 69 mg-per-tablespoon batch, 5 mg is about a seventh of a tablespoon - which tells you the honest problem with home edibles. Retail servings are dosed to 5 or 10 mg by testing and mixing equipment; a jar of homemade butter is dosed by arithmetic and hope. Start at the smallest portion your recipe divides into, not at a spoonful.
Why is the calculator's number a ceiling?
Three taxes the math cannot collect: decarb rarely reaches its theoretical percentage in a home oven that drifts; infusion leaves some THC behind in the plant matter you strain out; and a RTI Press review of cannabis edibles documents potency variation even in regulated products that are batch-tested. The calculator tells you the maximum the recipe can hit; assume the real batch is below it.
A measured batch starts with a controlled cycle
Every number above is only as good as "fully decarbed." The 2 in 1 Decarboxylator & Infuser 3oz runs both the dry cycle the calculator assumes and the 1-2 cup infusion in one 20 oz canister.
Herb Decarboxylator Green 2oz
2 oz dry / 10 oz liquid · 3 preset heat cycles
$99.99View product2 in 1 Decarboxylator & Infuser 3oz
3 oz dry / 20 oz liquid · Independent Decarb and Infuse modes
$129.99View product
Read next
- Cannabutter Dosing Chart: mg per Tbsp and CookieA cannabutter dosing chart with worked milligram math: mg per tablespoon and per cookie, the 0.877 conversion regulators use, and safe starting doses.
- Cannabutter Recipe: The Machine MethodA cannabutter recipe built around two stages: decarb at 240°F for 30-40 minutes, then infuse in butter at 160-190°F for 1-2 hours, strain, rinse, and set.
- Decarb Temperature Chart: Times and Temps That WorkA cannabis decarb temperature chart for flower, kief, hash, and hemp, with the research behind the numbers and where those numbers stop applying at home.