What the reaction removes
THCa carries a carboxyl group that distinguishes it from THC. During decarboxylation, that portion departs as carbon dioxide. The remaining molecule has less mass: THCa is 358.47 grams per mole, while THC is 314.46 grams per mole. The molecular ratio, 314.46 divided by 358.47, is approximately 0.877.
That mass change is easy to overlook because the label names differ by a single letter. Yet one gram of pure THCa cannot yield one gram of THC. Even under the formula’s ideal assumption of full conversion, only 87.7% of the starting THCa mass remains as theoretical THC. The lost portion did not vanish from the arithmetic; it left in a different chemical form.
Temperature and time work as a pair
Decarboxylation is not best understood as a single switch temperature. Heat supplies energy, and time determines how long the sample experiences that energy. A shorter, hotter event and a longer, gentler event are different routes through the same general reaction, with different opportunities for conversion across the material.
The important editorial distinction is between starting a reaction and completing it. Reaching a temperature for an instant does not prove that every THCa molecule in a dense or uneven sample has followed the same path. Conversely, lower heat sustained over time can continue changing the precursor. This is why device settings alone cannot be translated into an exact conversion percentage.
What a lighter does
A lighter creates an intense, localized heat source. Material directly at the flame encounters a rapid temperature rise, while nearby material warms through the moving hot zone. The result is a gradient rather than a uniform laboratory oven: distance from the flame, density, and airflow all change the time spent under heat.
That unevenness explains why “a flame was present” is not the same statement as “the entire sample converted completely.” The reaction may proceed at different rates from one part of the material to another. For label interpretation, the Total THC formula remains a theoretical comparison tool rather than a measurement of what one lighting event produced.
What a vape coil does
A vape coil transfers controlled electrical heat into the extract around it. Instead of a visible flame touching plant material, the oil warms against hardware whose setting and heat delivery shape the exposure. Compounds can begin evaporating below their published boiling points and continue leaving the liquid over time, so a boiling-point chart should not be treated as an on-off control panel.
The same caution applies to decarboxylation. A selected setting identifies the device’s target or operating level, not a guaranteed temperature for every microscopic part of the oil at every moment. Contact, flow, and duration determine the actual heating history. The coil’s job is energy transfer; the chemistry responds over time.
Conversion and evaporation are related to heat but they are not synonyms. Decarboxylation describes a molecular reaction in which THCa loses carbon dioxide and becomes THC. Evaporation describes molecules moving into the vapor phase. A heated sample can be undergoing both processes during the same interval, and a boiling-point reference addresses the second process more directly than the first. Keeping those verbs separate makes temperature discussions much clearer.
Why decarboxylation matters for potency math
A potency estimate that adds THCa and THC directly overstates the converted total because it ignores the mass released as carbon dioxide. The useful label equation is Total THC = (THCa × 0.877) + THC. It first converts the precursor into a THC-equivalent amount, then adds THC already measured in the sample.
For example, 70% THCa contributes a theoretical 61.39% THC after the mass adjustment. If the sample also contains 4% THC, its calculated Total THC is 65.39%. That number supports consistent label comparison and amount calculations. It still assumes full conversion of the THCa term, so it should be read as standardized chemical potential rather than a promise that every heating method will reproduce the total exactly.