How to Make Cannabutter: The Science of Decarboxylation, Infusion, and Dosing Math

Cannabutter is the foundation of cannabis edibles. It is also, done carelessly, the foundation of dosing disasters — the 200mg brownie that floors a guest, the batch that does nothing because the decarboxylation was wrong, the infusion that tastes like lawn clippings because the cook did not understand chlorophyll extraction.

Making good cannabutter is not difficult. But it is chemistry, and chemistry rewards precision. This guide covers the science at every step: why decarboxylation is non-negotiable, what actually happens during fat infusion, and how to calculate per-serving doses with reasonable accuracy.

Step Zero: Understanding What You Are Doing

Raw cannabis flower does not contain significant amounts of THC. It contains THCa (tetrahydrocannabinolic acid), a non-intoxicating precursor. THCa must be converted to THC through decarboxylation — the heat-driven removal of a carboxyl group (COOH) from the molecule.

This is not optional. If you skip decarboxylation and infuse raw flower directly into butter, your edibles will contain mostly THCa and will produce minimal psychoactive effect, regardless of how potent the flower was. Every failed batch of edibles that “didn’t work” traces back to one of two errors: insufficient decarboxylation or incorrect dosing math.

The second principle is fat solubility. THC is highly lipophilic — it dissolves readily in fats and oils but is essentially insoluble in water. Butter is approximately 80% milkfat, making it an effective extraction medium. The infusion process transfers THC from plant material into butterfat through passive diffusion driven by a concentration gradient.

With those two principles understood, the process becomes straightforward: decarboxylate the cannabis, infuse it into butter, strain out the plant material, and calculate your dose.

Step 1: Decarboxylation

Decarboxylation is a first-order kinetic reaction. The rate depends on temperature and time, and the relationship is well-characterized.

At room temperature, THCa decarboxylates extremely slowly — over months or years. Heat accelerates the reaction dramatically. But excessive heat degrades THC into CBN (cannabinol), a mildly sedating but far less psychoactive cannabinoid. The goal is to find the temperature sweet spot: hot enough to convert THCa to THC efficiently, but not so hot that THC degrades.

The optimal decarboxylation parameters, established through analytical chemistry studies and validated by multiple cannabis testing laboratories, are:

240 degrees F (115 degrees C) for 40 minutes in a standard kitchen oven.

This time-temperature combination achieves approximately 95% to 98% conversion of THCa to THC with minimal THC-to-CBN degradation (typically less than 5% loss). Some guides recommend higher temperatures for shorter times (e.g., 250F for 25 to 30 minutes), and these also work but have a narrower margin of error — the difference between optimal conversion and significant degradation at 250F is only a few minutes.

The procedure:

1. Preheat your oven to 240F. Use an oven thermometer to verify — kitchen ovens are notoriously inaccurate, and a 20-degree discrepancy is common.

2. Break your cannabis into roughly pea-sized pieces. You do not need to grind it finely; in fact, a fine grind increases surface area and can lead to more chlorophyll extraction later. Coarse breaking is sufficient for decarboxylation.

3. Spread the cannabis in a single layer on a parchment-lined baking sheet. Cover the sheet tightly with aluminum foil. This is important: the foil traps volatile terpenes and cannabinoids that would otherwise evaporate during heating, improving both potency and flavor.

4. Bake at 240F for 40 minutes. The cannabis should turn from green to a golden-brown color and become dry and crumbly. If it remains bright green, it is under-decarboxylated. If it is dark brown and smells burnt, you have overshot.

5. Remove from oven and allow to cool, still covered, for 10 minutes.

Your decarboxylated cannabis is now ready for infusion.

Step 2: The Dosing Math (Do This Before You Infuse)

This is the step most people skip, and it is the step most responsible for bad experiences. Before you make cannabutter, you need to know how strong it will be.

The formula:

(Grams of cannabis) x (THC percentage as a decimal) x 1000 = Total mg of THC available

Then apply an efficiency factor. Kitchen infusion does not extract 100% of available THC. Realistic extraction efficiency in a butter infusion is approximately 60% to 80%, depending on method and time. Use 70% as a reasonable middle estimate.

Example calculation:

You have 7 grams of cannabis flower tested at 20% THC.

• 7 x 0.20 x 1000 = 1,400 mg total THCa (pre-decarb)
• After decarboxylation (95% conversion, with the mass correction factor of 0.877 to account for the lost carboxyl group): 1,400 x 0.95 x 0.877 = approximately 1,166 mg THC
• After infusion at 70% efficiency: 1,166 x 0.70 = approximately 816 mg THC in your total butter batch

If you use 1 cup (2 sticks) of butter and your recipe makes 24 servings:

• 816 / 24 = approximately 34 mg THC per serving

For reference, a standard dispensary edible dose is 5 to 10 mg. A 34 mg per serving brownie is extremely potent and inappropriate for inexperienced consumers.

Adjustment strategies:

• Use less cannabis. For a moderate batch (approximately 10 mg per serving with 24 servings), you need roughly 2 to 3 grams of 20% flower per cup of butter.
• Use more butter. Spreading the same amount of cannabis across more butter reduces per-unit potency.
• Make the recipe yield more servings. Cut brownies smaller.

Do not eyeball this. Run the numbers. People who end up in emergency rooms after edible overconsumption almost universally skipped this step.

Step 3: The Infusion

You will need: your decarboxylated cannabis, unsalted butter (1 cup minimum), water, a saucepan or slow cooker, a fine mesh strainer or cheesecloth, and a container for the finished butter.

The stovetop method:

1. Combine 1 cup of butter and 1 cup of water in a saucepan. The water serves two functions: it prevents the butter from scorching (water keeps the mixture at 212F maximum), and it absorbs water-soluble compounds like chlorophyll that would otherwise make the butter taste unpleasant. The water will be separated out later.

2. Melt the butter over low heat, then add your decarboxylated cannabis. Stir gently.

3. Maintain the mixture at a very gentle simmer — between 160F and 200F — for 2 to 3 hours. Do not boil. Boiling temperatures accelerate THC degradation and produce more chlorophyll extraction. If you see active bubbling, your temperature is too high. A clip-on thermometer is invaluable here.

4. Stir occasionally. The THC is transferring from the plant material into the butterfat via passive diffusion. This is a slow process that benefits from time. Two hours is the minimum for good extraction; three hours is optimal. Beyond four hours, you get diminishing returns and increasing chlorophyll contamination.

The slow cooker method is identical but easier to maintain consistent temperature. Set your slow cooker to its lowest setting (most slow cookers on “low” maintain 170F to 190F, which is ideal), combine butter, water, and decarboxylated cannabis, and run for 3 to 4 hours with occasional stirring. This is the more foolproof method.

Step 4: Straining and Separation

1. Line a fine mesh strainer with cheesecloth (doubled over) and set it over a heat-safe bowl or container.

2. Pour the butter-water-cannabis mixture through the strainer slowly. Allow it to drain by gravity. Do not squeeze the cheesecloth. Squeezing forces chlorophyll, waxes, and fine particulate matter through the cloth, degrading taste and texture. You will leave behind a small amount of cannabinoid-containing butter, but the tradeoff in flavor and quality is worth it.

3. Discard the plant material.

4. Cover the bowl and refrigerate for at least 4 hours, or overnight. The butter will solidify on top of the water in a firm disk.

5. Remove the solid butter disk and discard the water underneath. The water will be green-brown and will carry the water-soluble compounds you do not want. Pat the bottom of the butter disk dry with a paper towel.

Your cannabutter is now finished. It will be yellow to light green in color. A strong green color indicates excessive chlorophyll extraction — still functional, but bitter. A golden-yellow color indicates a clean extraction.

Step 5: Storage

Cannabutter stores well. In an airtight container in the refrigerator, it will keep for 2 to 4 weeks. In the freezer, it keeps for 6 months or longer. THC is relatively stable in the absence of light, heat, and oxygen, and the butterfat matrix protects against oxidative degradation.

Label your cannabutter clearly — including the estimated total milligrams and the date of preparation. You do not want someone mistaking it for regular butter, and you will want the potency information when calculating recipe doses later.

Using Cannabutter in Recipes

Cannabutter substitutes 1:1 for regular butter in any recipe. The infusion does not change the cooking properties of the butter — it melts, emulsifies, and browns identically to regular butter.

The critical consideration is heat. THC begins to degrade above approximately 320F to 350F. Most baking occurs at 325F to 375F oven temperature, but the internal temperature of baked goods (the temperature the butter-containing matrix actually reaches) rarely exceeds 250F to 300F, even in a 375F oven. This means standard baking temperatures are generally safe for THC preservation.

However, stovetop cooking at high temperatures — sauteing, frying, or any application where the butter directly contacts a hot pan surface — can degrade THC. If you are using cannabutter for cooking rather than baking, keep temperatures below medium heat.

The Homogeneity Problem

The biggest challenge with homemade edibles is uneven distribution. In a batch of brownies, one piece may contain 15 mg of THC while the adjacent piece contains 40 mg. This is because THC-containing butterfat does not distribute uniformly through a batter unless thoroughly mixed.

To minimize this: mix your batter thoroughly and for longer than you normally would. Use recipes where the butter is fully emulsified into the batter (cakes, brownies, cookies) rather than recipes where the butter remains in discrete pockets (pastry, pie crust). Consider melting the cannabutter and mixing it with other liquid ingredients first before combining with dry ingredients.

Even with careful mixing, expect approximately plus or minus 20% to 30% variation between servings in a home kitchen. Professional edible manufacturers use mechanical homogenizers and analytical testing to achieve plus or minus 10% consistency. You do not have this equipment. Plan accordingly by targeting a moderate average dose, so that the variation between a “strong” piece and a “weak” piece remains within a comfortable range.

Quick Reference Dosing Guide

Based on 70% extraction efficiency and the standard formula:

Adjust proportionally for different THC percentages. If your flower is 25% THC instead of 20%, your total milligrams increase by 25%.

For beginners or low-tolerance individuals, target 5 to 10 mg per serving. For experienced users, 15 to 25 mg is a moderate dose. Doses above 50 mg are considered high and should be approached with caution even by experienced consumers. Our THC dosing guide covers what to expect at every dose level.

The golden rule of edibles: start low, wait two hours before redosing, and remember that you can always eat more but you cannot eat less.

Deep dive: Why Edibles Hit Different — The Neuroscience of Oral THC —>

Ready to put your cannabutter to use? See our complete guide to making edibles at home for gummy, brownie, and infused oil recipes.