Q10 Temperature Coefficient Calculator
Most biology sits between 2 and 3, which is the only reason the rule of thumb works at all.
The formula
Q10 = (R2 / R1) ^ (10 / (T2 - T1))
A rate multiplier per ten degrees
Q10 is the factor by which a rate changes for a ten-degree rise. Most biological processes sit between 2 and 3, which is why the rough rule that reactions double every ten degrees is useful at all. A purely physical process such as diffusion has a Q10 near 1.3, because it depends on temperature far more weakly than a chemical barrier does.
Its limits are biological, not mathematical
The exponential holds only while nothing breaks. Push a living system past about 40 degrees and proteins begin to denature, so the measured rate collapses rather than continuing to climb. Q10 is an empirical description of a narrow working range, and extrapolating outside it produces confident nonsense.
Related to activation energy
Q10 and the Arrhenius activation energy describe the same temperature dependence in different clothes. A Q10 of 2 near room temperature corresponds to a barrier of about 53 kJ/mol. Q10 is the form biologists reach for because it needs no assumption about mechanism.
Where these models stop
Michaelis-Menten assumes a single substrate and a steady state; Langmuir assumes one layer on identical sites with no interaction between them; Stokes-Einstein assumes a hard sphere much larger than the solvent molecules around it. Each is an idealisation that happens to describe real systems well over a useful range, and each fails predictably outside it. Knowing which assumption a number rests on is usually more valuable than the number.