THCa to THC Conversion Calculator

Precise molecular weight-based conversions for cannabis decarboxylation

Precise Calculation: Utilizes exact molecular weights (THCa: 358.47005 g/mol, THC: 314.46065 g/mol) for decarboxylation conversions. Conversion ratio: 0.87723 (~87.73%).
Conversion Calculator
Converted THC Amount
0.000g
After complete decarboxylation
CO₂ Released
0.000g
Mass Retained
87.7%
Weight Loss
0.000g
Batch Calculator
g
%
Frequently Asked Questions
What is the conversion ratio between THCa and THC?

The conversion ratio is based on molecular weights:

$$\text{Conversion Ratio} = \frac{\text{MW}_{\text{THC}}}{\text{MW}_{\text{THCa}}} = \frac{314.46065}{358.47005} = 0.87723$$
87.73% of THCa mass becomes THC

This means 1 gram of THCa produces 0.87723 grams of THC, with 0.1227 grams released as CO₂.

Why does weight decrease during decarboxylation?

During decarboxylation, THCa loses a carboxyl group (COOH) which is released as CO₂ gas:

$$\text{THCa} \xrightarrow{\text{Heat}} \text{THC} + \text{CO}_2$$
Decarboxylation reaction

The CO₂ molecule has a mass of 44.01 g/mol, which represents the 12.27% weight loss during complete conversion.

How do I calculate final THC percentage after decarboxylation?

If you start with a product containing X% THCa and Y% other compounds:

$$\text{Final THC\%} = \frac{X \times 0.87723}{(X \times 0.87723) + Y} \times 100$$
Final THC percentage formula

Example: 85% THCa + 15% other compounds → (85 × 0.87723) / ((85 × 0.87723) + 15) × 100 = 83.26% THC

Is this conversion 100% efficient in practice?

These calculations represent theoretical maximum conversion. In practice, conversion efficiency depends on:

Temperature: Optimal decarboxylation occurs around 220-240°F (104-116°C)

Time: Complete conversion typically requires 30-60 minutes at optimal temperature

Conditions: Some THC may degrade to CBN at higher temperatures or longer times

Real-world conversion efficiency is typically 85-95% of the theoretical maximum shown in these calculations.

Can I convert THC back to THCa?

No, decarboxylation is an irreversible chemical reaction. Once THCa loses its carboxyl group and becomes THC, it cannot naturally regain it to become THCa again.

The "THC → THCa" calculator is used to determine how much THCa was originally present before decarboxylation occurred, which is useful for:

• Calculating starting material amounts

• Understanding source material composition

• Planning batch production