THCa Percent Analyzer

Reverse-engineer THCa percentage from decarboxylation weight loss

Universal Extract Analyzer: This tool works for any THCa-dominant extract including rosin, BHO, live resin, hash, flower, and THCa isolate. By measuring CO₂ loss during decarboxylation, we can calculate the original THCa content with high accuracy.
Weight Loss Analysis
Critical Requirements Important
  • Use a precise, calibrated scale (recommended: 0.01g resolution or better).
  • Decarboxylate in a sealed, pressure-rated vessel to avoid terpene escape.
  • Allow the vessel to fully cool and then "burp" before final weighing.
  • Use a sample size that meets the Recommended minimum from the Precision & Sample Guide below.
g
g
Weight after decarboxylation is presumed complete (no more bubbling)
THCa PSI Chart
Before decarboxylation, calculate expected CO₂ production and ensure your sealed vessel can safely contain the pressure. Use pressure-rated vessels designed for this purpose. Never use glass jars not rated for pressure!
THCa PSI Calculator
Precision & Sample Guide
Accuracy Zone

Your scale's resolution dictates the minimum sample size required to detect the CO₂ weight loss signal.

Math Minimum: The smallest amount where weight loss is mathematically detectable ($\Delta m \ge 2r$).
Recommended: A safe amount that buffers against moisture and terpene errors ($\Delta m \ge 10r$).
Extract Type Avg. THCa Math Min. Recommended Viability
Frequently Asked Questions
How does this calculator work?

Mathematical Foundation:

$\text{THCa} \xrightarrow{\text{heat}} \text{THC} + \text{CO}_2$
$358.47 \text{ g/mol} \rightarrow 314.46 \text{ g/mol} + 44.01 \text{ g/mol}$
Stoichiometric decarboxylation reaction

The calculator uses stoichiometry to work backwards from CO₂ weight loss:

  1. Measure weight loss = CO₂ released during decarboxylation
  2. Calculate moles of CO₂ = weight loss ÷ 44.01 g/mol
  3. Calculate original THCa = moles CO₂ × 358.47 g/mol (1:1 ratio)
  4. Calculate percentage = THCa weight ÷ initial sample weight

Best Accuracy with Concentrates:

This method works most accurately with isolates, resin, rosin/BHO, shatter, and hashHigh-purity extracts (>70% cannabinoids) provide the most reliable results.

Flower Analysis - Possible but Complex:

This technique can work for flower if you're certain complete decarboxylation occurred, but requires understanding the limitations:

  • Moisture content must be completely eliminated first (pre-dry at 180°F)
  • Plant material contains cellulose, lignin, and other compounds that may degrade at decarb temperatures
  • Expected range for flower: 15-30% THCa (vs 70-95% for concentrates)
  • Larger samples needed (minimum 10-20g) due to lower cannabinoid density

Terpene Volatilization - Critical Limitation:

The biggest source of error comes from terpene evaporation, which falsely increases apparent weight loss:

$\text{Measured Loss} = \text{CO}_2 + \text{Terpenes} + \text{Other Volatiles}$
Why sealed vessels are essential
  • Live resin/flower: High terpene content (5-15%) can significantly skew results upward
  • Cured extracts: Lower terpene content (1-5%) provides better accuracy
  • THCa isolate: Minimal terpenes (<1%) gives highest precision

Temperature Considerations:

Too low (below 200°F): Incomplete decarboxylation, false low results
Too high (above 250°F): THC degradation to CBN, false high results
Optimal: 220-240°F for consistent, accurate results

Bottom Line: This method is most reliable for concentrates and extracts where cannabinoids comprise the majority of the material. For flower or high-terpene extracts, expect some margin of error due to volatile compound loss.
How accurate is this compared to lab testing?

When performed correctly, this method can achieve accuracy within ±2-5% of lab results for high-purity extracts.

Comparison to Lab Methods:

  • HPLC (High-Performance Liquid Chromatography) - Lab standard, ±1% accuracy, $50-100 per test
  • This Method (Weight Loss) - ±2-5% accuracy with proper technique, essentially free
  • GC-MS (Gas Chromatography-Mass Spectrometry) - ±2% accuracy, $100-200 per test

Advantages of This Method:

  • Free (no lab fees)
  • Immediate results
  • No sample submission/waiting
  • Based on fundamental chemistry (stoichiometry)
  • Works anywhere with basic equipment

When to Use Lab Testing Instead:

  • Regulatory compliance/legal requirements
  • Need full cannabinoid profile (not just THCa/THC)
  • Testing for contaminants/pesticides
  • Commercial product labeling
  • Research requiring documented chain of custody
Why must the vessel be sealed?

Sealing the vessel is critical for accurate results because:

1. Prevents Material Loss

During decarboxylation, terpenes and other volatile compounds can evaporate. If the vessel is open, these escaping compounds add to the weight loss, making it appear you had more THCa than actually present.

2. Ensures Only CO₂ Loss is Measured

$\text{Weight Loss}_{\text{sealed}} = \text{CO}_2 \text{ only}$
$\text{Weight Loss}_{\text{open}} = \text{CO}_2 + \text{terpenes} + \text{moisture} + \text{other volatiles}$
Sealed vs. open vessel weight loss

3. Safety Considerations

The sealed vessel also serves a safety purpose:

  • Contains any pressure buildup safely
  • Prevents splattering of hot material
  • Reduces fire risk from vapor ignition

Proper Sealing Techniques:

  • Mason Jars: Use pressure-rated jars with new lids
  • Lab Glassware: Rubber septa or ground glass stoppers
  • Specialized Vessels: Pressure-rated containers with relief valves
Important: After cooling, "burp" the vessel by briefly opening to release CO₂ pressure, then reseal before final weighing. This prevents trapped CO₂ from affecting the weight measurement.
What if my results seem wrong?

Results Higher Than Expected?

Possible causes:

  • Moisture Loss - Sample wasn't completely dry before testing
  • Solvent Loss - BHO/extract had residual solvents that evaporated
  • Open Vessel - Terpenes/volatiles escaped, increasing apparent weight loss
  • Incomplete Cooling - Weighed while still warm (thermal expansion affects weight)

Results Lower Than Expected?

Possible causes:

  • Incomplete Decarboxylation - Temperature too low or insufficient time
  • Trapped CO₂ - Didn't burp the vessel after cooling
  • Material Already Decarbed - Sample contained THC instead of THCa
  • Scale Drift - Scale wasn't calibrated or drifted during test

Verification Steps:

  1. Repeat the test with a fresh sample
  2. Calibrate your scale before testing
  3. Ensure sample is completely dry (can pre-dry in oven at 180°F)
  4. Verify temperature is stable at 220-240°F throughout
  5. Ensure complete decarboxylation (no more bubbling)
  6. Compare to expected range for your extract type

Typical Ranges by Extract Type:

  • THCa Isolate: 95-99%
  • BHO/Shatter: 70-90%
  • Rosin: 60-85%
  • Hash: 40-70%
  • Flower: 15-30%
Can I use this for CBD or other cannabinoids?

This calculator is specifically designed for THCa analysis and will not give accurate results for other cannabinoid acids.

Why THCa Only?

The calculator uses the specific molecular weight of THCa (358.47005 g/mol). Other cannabinoid acids have different molecular weights:

  • CBDa: 358.47 g/mol (same as THCa, so technically works!)
  • CBGa: 360.49 g/mol (2g/mol difference)
  • CBCa: 358.47 g/mol (same as THCa)
  • THCVa: 330.42 g/mol (28g/mol difference - significant error)

For CBDa Analysis:

Good news! CBDa has nearly identical molecular weight to THCa, so this calculator will work with similar accuracy. Just substitute "CBDa" for "THCa" in your interpretation.

For Mixed Cannabinoid Profiles:

If your extract contains significant amounts of multiple cannabinoid acids, results will be an average weighted by the molecular weights. This is less accurate but still provides useful information about total acidic cannabinoid content.

Future Development:

A multi-cannabinoid version would require additional inputs or advanced analysis beyond simple weight loss measurement.