This is not a calculator for the customer. It is for whoever is standing over the scale with an extract and its certificate of analysis, a canister of carrier oil, and a figure that has to end up on the label. The three sums you repeat every time are here ready-made — and each one comes with the formula written out, so you can check it on paper.
Everything runs in your own browser. No sign-in, no account, nothing sent to a server — the numbers you type here go nowhere. The tools are free and will stay free, competitors included. Quality in this trade grows when the arithmetic is right.
Diluting an extract
How much extract and how much carrier oil a batch needs to reach a target CBD content — and how much THC is left in it.
The basic production sum. Enter what the certificate of analysis says about the extract, what the finished oil should contain and how large a batch you want. Add the THC in the extract and you also get the THC in the result — dilution brings it down in exactly the same proportion as the CBD.
How this is calculated
The third line is only the first line written differently: the extract makes up the same share of the batch for every compound it carries, so THC falls in the same proportion as CBD. Dilution never raises a content — which is why the target cannot exceed what is in the extract.
Extract and isolate combined
When two figures have to hold at once — high CBD and low THC. For experienced users.
Dilution alone never changes the ratio of CBD to THC; if you need more CBD and less THC than that ratio allows, a third material has to enter the mixture — an isolate. The tool solves a system of two equations and tells you how much extract, how much isolate and how much carrier oil to weigh out.
How this is calculated
E is the extract you are looking for, I the isolate. Two unknowns and two conditions, so the system has exactly one solution — we compute it directly, through the determinant. It fails to exist only when the isolate carries the same CBD-to-THC ratio as the extract; then nothing you add can shift that ratio. And if one of the figures comes out negative, that mixture cannot be made from these two materials — you need a cleaner isolate or an extract lower in THC.
Total CBD
The acid form and the decarboxylated one added up — the figure an analysis reports as “total CBD”.
In the plant and in a raw extract most of the CBD is still in its acid form, CBDA. Heating sheds carbon dioxide from it and leaves CBD — but not gram for gram, because part of the mass leaves as gas. Total CBD is therefore CBD plus 0.877 times CBDA.
How this is calculated
The 0.877 is the ratio of the molar masses of CBD (314.5 g/mol) and CBDA (358.5 g/mol). One gram of CBDA therefore yields 0.877 grams of CBD once fully decarboxylated; the rest leaves as carbon dioxide. The same conversion, with the same number, holds for the THCA and THC pair.
- % w/w
- Percent by weight — how many grams of a substance sit in 100 grams of the mixture. Analyses of extracts and oils are reported this way, not by volume. That is why everything on this page is counted in grams, never millilitres.
- Extract
- The concentrated output of the plant. Along with the compound you want it carries everything else that came through, THC included. That is why dilution has to be watched for two compounds at once.
- Isolate
- A single compound in pure form, usually above 98 %. It lifts the CBD without bringing THC along — which is exactly what the second tool is for.
- Carrier oil
- The oil the extract is dissolved in — hemp, MCT, olive. In the mass balance it is the material that fills the batch up to its total weight and contributes no active compound of its own.
- Decarboxylation
- The heating step in which CBDA sheds carbon dioxide and becomes CBD. It is the reason total CBD cannot be worked out by plain addition — and the reason the third tool exists.
How do I work out how much extract an oil of a given CBD content needs?
Extract = batch weight × target CBD content ÷ CBD content of the extract. For 1000 g of 5 % CBD oil from a 60 % extract you need 83.333 g of extract and 916.667 g of carrier oil. It is counted in grams, because analyses are reported as percent by weight (% w/w).
Does dilution bring the THC down as well?
Yes, and in exactly the same proportion as the CBD. The extract enters the mixture as a whole, so every compound in it is diluted equally. The ratio of CBD to THC therefore never changes through dilution alone — shifting it takes an isolate.
Why is total CBD calculated with the number 0.877?
It is the ratio of the molar masses of CBD (314.5 g/mol) and CBDA (358.5 g/mol). During decarboxylation the CBDA molecule sheds carbon dioxide, so one gram of the acid form yields 0.877 grams of CBD. Total CBD = CBD + 0.877 × CBDA. The same number applies when converting THCA to THC.
What does % w/w mean?
Percent by weight to weight — how many grams of a substance there are per 100 grams of mixture. It is not the same as percent by volume, nor as milligrams per millilitre; oils have a density below 1 g/ml, so converting through volume gives a different figure.
How do I blend an oil that is high in CBD and low in THC at the same time?
By combining extract with isolate. There are two unknowns — the amount of extract and the amount of isolate — and two conditions, the target CBD and the target THC. The system has exactly one solution; if it comes out negative, that blend cannot be made from those two materials and you need a cleaner isolate or an extract lower in THC.
Are the numbers I type into the calculators stored?
No. The whole calculation runs in the browser on your own device, nothing is sent to a server and nothing is saved. The site uses no analytics or tracking cookies.
The calculation is an aid, not a guarantee. It works from the numbers you put into it — an imprecise analysis gives an imprecise result. What the finished batch actually contains is confirmed by a laboratory analysis of the finished oil, not by a calculator.
The mass balance assumes the extract and the isolate dissolve fully in the oil and that nothing is lost. In practice some material stays on the walls of the vessel and on the stirrer; with small batches that is worth allowing for.
Check the permitted contents against the product category and the country where you place the product on the market. CBDICAL gives no legal opinion on this and takes no responsibility for decisions made on the basis of figures calculated on this page.
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