The chain of losses
Getting from a gram of concentrate to a known dose per gummy is not one calculation. It's a chain, and each link takes a cut. Miss any of them and your estimate comes out high.
The first loss is chemical and unavoidable. Decarboxylation converts THCA to THC by driving off CO₂, and that gas takes 12.3% of the mass with it. This is fixed by molecular weight, not by technique.
THC = THCA × (314.47 ÷ 358.48) = THCA × 0.877
The second loss is how completely that conversion happens. Home decarb is rarely total - too cool and you leave THCA unconverted, too hot for too long and you start degrading THC into CBN. Something in the region of 90% is a reasonable working assumption for a decent oven decarb.
The third loss is infusion. THC is fat-soluble, so it transfers into butter or oil, but not perfectly. Some stays behind on plant matter and equipment. With a concentrate rather than flower this is more efficient than usual, since there's no plant material to hold onto, but you still lose some to the vessel.
Why concentrate is easier than flower
Working from rosin or shatter removes most of the guesswork that makes flower-based edibles unpredictable. You have a lab-tested percentage on the label, there's no plant matter to absorb and retain oil, and the potency is uniform through the material.
With flower you're estimating potency from a strain name, guessing at how much survived decarb in an uneven oven, and losing an unknown quantity to the plant material itself. That's three compounding unknowns. With concentrate you have one lab figure and two efficiency estimates.
Running the calculator backwards
The more useful direction for most people is the reverse. You know you want 10 mg gummies and you're making 60 of them - the question is how much rosin to weigh out.
That's the same chain inverted. Total THC needed is dose times servings. Divide by infusion retention to get what must go in before that loss, then divide by the effective potency per gram to get your weight.
grams = (dose × servings ÷ infusion) ÷ (mg THC per gram)
Does yours need decarbing?
Almost all of them do. The two exceptions are the ones already heated during manufacture, and putting those through a second decarb only degrades them. Get this wrong in either direction and the batch comes out either useless or unexpectedly harsh.
| What you have | Decarb first? | Why |
|---|---|---|
| Live rosin | Yes | Pressed cold to keep terpenes, so it stays almost entirely THCA |
| Cured rosin | Yes | Pressing temperature is well below the decarb range |
| Live resin | Yes | Extracted cold for the same reason |
| Shatter, budder, badder, wax | Yes | Purged below decarb temperature |
| Crumble | Yes | Warmer, longer purge, but rarely converts fully |
| THCA diamonds, sauce | Yes | Close to pure THCA - the worst one to skip |
| Kief, dry sift, bubble hash | Yes | Raw trichomes, entirely unheated |
| Distillate | No | Already activated by the heat of distillation |
| RSO, FECO | No | Activated while the solvent is heated off |
The test that beats any list
Read the certificate of analysis rather than the product name, because names are used inconsistently between producers. The numbers say it plainly.
High THCA, low THC - raw, needs decarbing. Something like 78% THCA against 2% THC is the typical signature.
High THC, near-zero THCA - already activated. Leave it alone, and set decarb efficiency to 100% here since there's nothing left to convert.
If your label gives only a single Total THC figure, switch the potency dropdown to Total THC. That number already has the conversion baked in, and the decarb setting stops applying to it.
What happens if you skip it
THCA isn't psychoactive. Infusing raw rosin straight into butter gives you an edible that does very little, and people usually conclude the recipe failed rather than that the chemistry never happened.
What happens if you decarb something twice
The opposite problem, and a quieter one. Distillate and RSO have already been through it, so more heat doesn't add potency - it degrades THC toward CBN, which is more sedating and less potent. You lose a little strength and gain grogginess.
Edibles dosage questions
Why is 0.877 used instead of just the THCA percentage?
Because THCA and THC are different molecules with different weights. THCA is 358.48 g/mol and THC is 314.47 g/mol. When the acid group leaves as carbon dioxide, the remaining molecule is lighter by that ratio. So a gram of pure THCA yields 0.877 g of THC and 0.123 g of CO₂, no matter how good your technique is.
My label just says 82% THC. Which box do I use?
Use the Total THC option. Nearly all lab reports that give a single figure have already applied the conversion, using THC + (THCA × 0.877). Entering that number as THCA would apply the discount a second time and leave your estimate about 12% low.
Do I need to decarb concentrate before infusing?
It depends on what you have. Live rosin and most shatter are largely THCA and need decarbing. Distillate is usually already activated, which is why it's often sold as a straight infusion ingredient. If your label shows a high THC and near-zero THCA, it's already decarbed - set decarb efficiency to 100% since there's nothing left to convert.
What infusion retention should I assume?
With concentrate into fat, somewhere between 80 and 95% is realistic, and it's better than flower because nothing is absorbing your oil. The default here is a deliberately conservative 80%. If you're confident in your process, raise it and see how the answer moves - that spread is the honest uncertainty in the whole calculation.
How many gummies should I make?
However many your mold holds - and there's no standard. Cavity counts run from about 35 to nearly 400 depending on the tray, so any calculator that defaults to a specific batch size is inventing it. That's why this page asks for the dose you want first and then tells you how far your material actually stretches. Count your own mold, put that number in, and the readout tells you whether you have enough to fill it at your target dose or whether you're short.
Why did my gummies come out uneven?
Mixing, not maths. Cannabis oil and water-based candy bases separate readily, and THC is not water-soluble. Without an emulsifier and thorough stirring right up to the point of pouring, the oil concentrates in part of the batch. The calculator gives you a batch average - it cannot tell you how evenly that average is spread.
Can I use this for flower instead of concentrate?
The arithmetic works if you enter flower's percentages, but the answer will be much less reliable. Flower potency varies within the same jar, decarb is less even, and plant material retains a meaningful and unpredictable share of the oil. Treat any flower-based figure as a rough upper bound.