Decarboxylation: temperature, time and the 0.877 factor
Why raw flower does almost nothing in butter, what heat does to THCA, and the oven setting every infusion on this site uses.
What decarboxylation is
Fresh and cured cannabis flower contains very little THC. Most of it is THCA, tetrahydrocannabinolic acid, which is not intoxicating. Heat removes a carboxyl group from the THCA molecule as carbon dioxide and leaves THC behind. Smoking and vaporising do this instantly; cooking has to do it deliberately, because the temperatures inside a brownie or a pan of butter are too low and too brief to finish the job on their own.
The conversion also loses mass. THCA has a molar mass of about 358.5 g/mol and THC about 314.5 g/mol (PubChem), so one gram of THCA can become at most 0.877 g of THC. That is the 0.877 in every dose calculation on this site.
Temperature and time
Decarboxylation is a trade-off. Hotter and longer converts more THCA, but THC itself degrades with heat, mostly to CBN, which is far less potent. A 2016 kinetics study (Wang et al.) measured these reactions across the 80–145 °C range and found that THCA converts within tens of minutes at the lower end of that range while longer or hotter heating starts to consume THC. The practical window most home guides settle on is 115–120 °C for 30–40 minutes: Leafly's cannabutter guide (updated 2026-05-05) uses 118 °C (245 °F) for 30–40 minutes, and the infusion recipes here use 115 °C (240 °F) for 35–40 minutes, the lower end of the same window.
| Oven | Time | Result |
|---|---|---|
| 105 °C / 220 °F | 45–60 min | Gentler; slightly less complete conversion, less aroma loss |
| 115 °C / 240 °F | 30–40 min | The standard used on this site |
| above 130 °C / 265 °F | any | Conversion is fast but THC degrades and terpenes burn off; avoid |
How to do it
- Heat the oven to 115 °C (240 °F). Domestic ovens are often 10–15 °C off; an oven thermometer is worth having.
- Break the flower into pea-sized pieces by hand. Grinding fine makes it easy to scorch and hard to strain later.
- Spread in one layer on a baking-paper-lined tray. Cover loosely with foil if you want to limit the smell.
- Bake 35–40 minutes. It should look dry and slightly darker, like toasted herbs, not brown.
- Cool completely before adding to butter, oil or alcohol. Hot flower in cold alcohol is a fire risk.
Common mistakes
- Skipping it because the recipe bakes anyway. A brownie's interior stays well under 100 °C; it will not finish the conversion.
- Grinding to powder. It scorches, and the powder passes through cheesecloth into the finished infusion.
- Using the microwave or a frying pan. Neither holds a steady low temperature.
- Assuming 100% conversion. The calculator assumes it, which is deliberate: it makes every dose figure on this site a maximum, and the real figure is at or below it.
What about CBD?
CBDA decarboxylates to CBD by the same mechanism and in the same temperature range, with a slightly different mass factor (0.877 is specific to THCA→THC). If your flower is CBD-dominant, use the THC fields in the calculator for the THC it does contain and treat the CBD separately; CBD is not what the dose limits here are about.
- PubChem, National Library of Medicine: Dronabinol (THC), CID 16078, molecular weight 314.5 g/mol, pubchem.ncbi.nlm.nih.gov/compound/16078; Tetrahydrocannabinolic acid, CID 98523, molecular weight 358.5 g/mol, pubchem.ncbi.nlm.nih.gov/compound/98523. Accessed 2026-11-14.
- Wang M, Wang Y-H, Avula B, et al. Decarboxylation Study of Acidic Cannabinoids: A Novel Approach Using Ultra-High-Performance Supercritical Fluid Chromatography/Photodiode Array-Mass Spectrometry. Cannabis and Cannabinoid Research. 2016;1(1):262–271. doi:10.1089/can.2016.0020.
- Leafly, How to make cannabutter (decarboxylate at 245 °F / 118 °C for 30–40 minutes; its calculator applies an 87.7% THCA→THC conversion), last updated 2026-05-05, leafly.com/learn/consume/edibles/how-to-make-cannabutter. Accessed 2026-11-14.
