THCA vs THC: what the numbers on a cannabis lab report really mean
Most flower is labelled with its THCA figure, but THCA isn’t THC. Put your own numbers in the calculator and see the difference in seconds.
CANNAVEC EDITORIALCHECKED AGAINST THE CANNABIS KNOWLEDGE BASEUPDATED 8 MIN READ
Total THC calculator
24.80 × 0.877 + 0.60 = 22.35%. Adding them overstates it by 3.05 points.
The short answer
THCA is the acid form of THC that raw cannabis makes. It does not cause a high until heat turns it into THC, and it loses about 12% of its weight on the way. That is why labs calculate Total THC as THCA × 0.877 + Δ9-THC. A flower listed as 24.8% THCA and 0.6% THC holds about 22.4% Total THC, not 25.4%.
- The 0.877 factor is chemistry: THC’s molecular weight divided by THCA’s.
- US hemp law writes the formula in: Total THC above 0.3% is not hemp (US Department of Agriculture Final Rule, 2021).
- Independent retesting often finds less THC than the label says (Schwabe et al., 2023).
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Why it matters
The number on the jar is not always the number in the jar.
A Colorado study bought retail flower and sent it for independent testing. The average came back at about 15% THC, against labels that clustered around 20%.
Labs also differ from each other. In Washington State’s full testing dataset, reported THC varied systematically depending on which lab did the test, even for the same producers and strains (Jikomes and Zoorob, 2018). A certificate of analysis (COA) is evidence, and evidence is worth checking.
Colorado retail flower, THC %
The lab method changes the answer
Liquid chromatography keeps THCA and THC apart. Gas chromatography quietly merges them.
Labs measure cannabinoids with one of two kinds of machine: high-performance liquid chromatography (HPLC) or gas chromatography (GC). Both separate a sample into its compounds. The difference is heat.
HPLC · HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY
Two separate readings
Runs cool, so THCA and THC show up as two numbers. Total THC is then calculated with the 0.877 factor. This is the method pharmacopoeias recommend for potency.
GC · GAS CHROMATOGRAPHY
One blended reading
The hot injector converts THCA as the sample goes in, often only partly. You get a single THC number that can read several points lower than liquid chromatography on the same flower.
Takeaway: only compare Total THC figures produced by the same method. Your certificate of analysis should say which one was used.
Read the whole page
A certificate of analysis has five parts. Most people read one.
Pick a part of the certificate to see what it tells you, what it can’t, and the red flag to look for.
Cannabinoids
WHAT IT TELLS YOU
THCA, THC, CBDA, CBD and minor cannabinoids, from which Total THC and Total CBD are calculated.
WHAT IT CAN’T TELL YOU
How a person will feel. Total THC is a ceiling, not a prediction.
RED FLAG
Total THC that does not equal THCA × 0.877 + Δ9-THC, or above about 35% in dried flower.
Let our agent read it for you
Drop in a certificate of analysis. Watch the agent write the report.
Everything this article teaches you to check, we built an AI agent to check for you. The Cannavec COA Report agent takes the PDF your lab sends, reads every table on it and writes a full report in eight sections: the maths, the terpenes, the strain fingerprint, the evidence, the gaps.
COA Report
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Drop a Certificate of Analysis PDF here, or click to browse
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Cannavec · COA Report
Wedding Cake
Dried flower · full-panel certificate · Quebec lab
01Cannabinoids
THCA36.4%Δ9-THC0.25%Total THC32.2%02Terpenes
Limonene 0.76%Myrcene 0.51%trans-Nerolidol 0.48%β-Caryophyllene 0.45%Total 3.06%03Chemovar fingerprint
82% match, Gold tier
1,247 archived samples, 10 labs04Indicated profile
AChronic and inflammatory painBMuscle relaxation, evening sleep!Anxiety: caution05Clinic guidance
For THC-experienced patients. Not for the anxiety-prone or THC-naïve: there is no CBD buffer.
06Market position
32.2% THC against a UK comparator ceiling of 28%.
07Price recommendation
Floor £7.50/gTarget £8.75/gCeiling £9.75/g08Contaminants
Heavy metals ✓Aflatoxins ✓~90 pesticides ✓No microbial panel
Your report appears here
Figures from a real COA Report, published as a sample. Not for clinical or commercial use.
IT CHECKS THE MATHS
Every Total THC and Total CBD figure is recalculated from the raw results, and any mismatch is flagged.
IT READS ANY LAB
Basic, basic plus and full-panel certificates, in any source language, with the certificate type detected for you.
IT SHOWS ITS WORKING
Its chemistry is compared with nearly 3,000 strain fingerprints, and every evidence claim is graded A, B or C and cited.
Cannavec does not test cannabis. The agent reads the results an accredited laboratory produced.
For cannabis businesses
Put certificate checks inside your own systems. Our engineers do the work.
You don’t need a development team of your own. Cannavec’s engineers install the COA Report agent on your website or inside your stock or clinic software, connect it to your own product data, dress it in your colours and keep it running.
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Cannavec engineers sit with your team, on your systems.
01 · INSTALL & CONNECT
On your site, reading your data
Embedded in your pages in your colours, and pointed at your product, batch or patient records, so every certificate is checked where it already lives.
02 · MAINTAIN
Kept current for you
We keep it running and up to date as regulations and the evidence change.
Who it’s for
CLINICS
Evaluate products before you prescribe
A consistent, cited summary of every product on your formulary, ready for your prescribers.
PHARMACIES & DISTRIBUTORS
Check every certificate on arrival
Spot missing contaminant results, maths that doesn’t add up and old test dates before stock moves.
CULTIVATORS
See how a harvest compares
Benchmark each batch against its strain’s fingerprint and see where it sits on price.
Our engineers, inside your team.
See how integrations work and how embedded engineering is priced, or tell us what you need and we’ll scope it with you. We also train your team to read certificates of analysis and to work well with AI agents.
Questions people ask
THCA and THC, answered.
Is THCA stronger than THC?
No. THCA itself barely acts on the CB1 receptor, the one behind THC's effects. Once heated, 1 mg of THCA becomes about 0.88 mg of THC. A high THCA figure means a lot of potential THC, not a stronger compound.
Why does my COA show more THCA than THC?
Fresh cured flower holds most of its THC as THCA, typically 90–95%. Only a small share has already converted during drying and curing.
How do I calculate Total THC from a COA?
Multiply the THCA figure by 0.877 and add the Δ9-THC figure. The same rule gives Total CBD from CBDA and CBD.
Does Total THC tell me how strong the effect will be?
Only partly. It is the maximum THC the product can deliver. How it is used, the other cannabinoids and terpenes present, and the person all matter. This is information, not medical advice.
Is Cannavec a testing lab?
No. Cannavec builds AI agents for the cannabis industry. The COA Report agent reads certificates produced by accredited laboratories and turns them into evidence-graded reports.