How to Decarb Cannabis: 240°F for 30–40 Minutes, Step by Step

TL;DR

Raw cannabis flower contains THCA, which is not intoxicating when eaten. Heating it — decarboxylation — converts THCA into THC. In lab testing, THCA was almost completely converted after about 30 minutes at 230°F, with only about 8% of the THC lost. For a home oven, 240°F (115°C) for 30 to 40 minutes is the reliable standard for dried flower. CBD flower needs roughly twice as long, because CBDA converts at about half the speed of THCA.

What decarboxylation actually is

Cannabis plants don't make much THC directly. They make THCA — THC with an extra carboxyl group attached — and that small attachment changes everything: eaten raw, THCA passes through without producing a high. Heat breaks the carboxyl group off (it leaves as carbon dioxide), and what remains is THC.

Smoking and vaping do this instantly at high temperatures. Baking does it slowly and on purpose, before the flower ever meets butter or oil. Skip the step and your edibles will be weak no matter how good the flower was — the single most common reason homemade edibles disappoint.

One ceiling worth knowing: THC weighs less than THCA, so even a perfect conversion yields at most about 87.7% of the starting THCA by weight. That 0.877 factor is the same one used to calculate total THC on lab labels — we break it down in our guide to what THC percentage actually means.

The lab numbers: temperature vs. time

The reference study (Wang and colleagues, 2016, published in Cannabis and Cannabinoid Research) heated cannabis extract at controlled temperatures and tracked the conversion:

• Below 212°F (100°C): conversion did not finish even after 60 minutes.
• 230°F (110°C): THCA almost completely converted in about 30 minutes, with roughly 8% of the resulting THC lost.
• 266°F (130°C): conversion in about 9 minutes — faster, with less margin for error.
• 293°F (145°C): conversion in about 6 minutes, but THC levels peaked and then started falling as heat began degrading it.

Home ovens heat less evenly than lab equipment and flower has to warm through, which is why kitchen guidance lands a little hotter and longer than the lab minimum: 240°F for 30 to 40 minutes. Dense or slightly moist buds may need 40 to 50 minutes.

Step-by-step: the oven method

1. Preheat to 240°F — and verify it. Oven dials are commonly off by 25°F or more. An inexpensive oven thermometer removes the guesswork, and temperature is the whole game here.
2. Break the flower up coarsely. Use your fingers or scissors to make pea-sized pieces. Don't grind it to powder — fine powder exposes more surface to heat and is easier to scorch.
3. Spread it in a thin, even layer on a parchment-lined baking sheet, or in an oven-safe glass dish. A crowded, heaped layer heats unevenly.
4. Cover loosely with foil (or use a lidded oven-safe dish). This keeps the temperature steadier and holds in some of the aroma.
5. Bake 30 to 40 minutes. Stir or gently shake the tray once, halfway through, for an even conversion.
6. Check the color. Done flower is light to medium golden brown, dry and crumbly, with a toasty smell. Pale green means it needs more time; dark brown means it went too far.
7. Cool completely before using. From here it can go into butter or oil for infusion, into a recipe, or into an airtight jar for later.

Other methods

Mason jar method (less smell)

Put the broken-up flower in a mason jar with the lid on finger-tight, lay the jar on its side on a baking sheet, and bake at the same 240°F for 30 to 40 minutes, shaking gently once halfway. The sealed jar noticeably reduces the smell and keeps the flower from drying out further. Let the jar cool before opening it.

Sous vide (most precise, no smell)

Vacuum-seal the flower and immerse it in a water bath. Most home guides land near 200°F for about 90 minutes — below boiling, so conversion is slower but very even, and the sealed bag contains the aroma almost completely.

Decarbing CBD flower

The same step activates CBD: raw hemp and CBD flower carry CBDA, and heat converts it to CBD. In the same 2016 study, CBDA converted at about half the rate of THCA — so give CBD flower roughly twice the time at the same temperature (about 60 to 80 minutes at 240°F), and check color the same way.

What goes wrong

• Too hot. Past roughly 290°F, THC degrades quickly once conversion finishes — some of it becomes CBN, which is mostly sedative. Hotter is not better; it is just faster past the peak.
• Too cool or too short. Under about 212°F, an hour still won't finish the job. Undercooked flower makes weak edibles.
• Trusting the dial. A 25°F error is the difference between the two mistakes above. The thermometer is the fix.
• Walking away. Flower can go from golden to scorched in the last few minutes. Stay nearby for your first batch and note your oven's real timing.

The dosing math, before you infuse

Decarbed flower's maximum possible THC is simple to estimate:

Flower weight (mg) × THCA % × 0.877 = maximum THC in mg

Example: an eighth (3.5 g = 3,500 mg) of flower at 22% THCA holds at most 3,500 × 0.22 × 0.877 ≈ 675 mg THC in the whole batch. Home decarbing and infusion never capture 100% of that, so treat 675 mg as a ceiling, not a serving chart — if that batch becomes 24 cookies, each one is at most ~28 mg, and honestly less. Label the batch, and start with a small piece: our low-dose edibles guide explains how to find a 1 to 2.5 mg starting dose. Decarbed flower you don't use right away keeps best the same way as any flower — see how to store flower so it stays fresh.

Our perspective

Decarbing is worth doing well if you enjoy making your own — it is the difference between edibles that work and edibles that waste good flower. It is also, honestly, the fiddly part: an oven that's off by 25 degrees and a batch whose real strength you can only estimate. That's exactly the problem licensed edibles solve — every product we deliver is lab-tested with the dose printed on the label, no thermometer required. Plenty of our customers keep a foot in both camps: homemade butter for the fun of it, labeled edibles when the dose actually matters.

FAQ

Do you have to decarb cannabis before making cannabutter?

Yes, for the butter to be potent. Simmering flower in butter does apply heat, but infusion temperatures are usually too low and uneven to finish the conversion. Decarb first, then infuse — the two steps do different jobs.

What happens if you eat raw cannabis?

Very little, for most people. Raw flower's cannabinoids are mostly THCA, which is not intoxicating when eaten. You would digest some plant nutrients and terpenes, but not a high.

Does decarbing make your house smell?

Some, with the open-tray method — it is a warm, toasty cannabis smell that fades within a few hours. The mason jar method cuts it significantly, and sous vide contains it almost entirely.

Can you decarb in an air fryer or toaster oven?

Yes — the same 240°F and 30 to 40 minutes works, in smaller batches. Use the thermometer if you can; small appliances swing temperature more than full-size ovens, so check the color a few minutes early.

How long does decarbed flower stay good?

Stored airtight in a cool, dark place, decarbed flower keeps its potency for weeks to a few months. It dries out faster than fresh flower, so most people infuse it into butter or oil within a few days — the infusion keeps longer than the flower does.

Sources

• Wang M, Wang YH, 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.