In our pursuit to further improve the scalability of photocatalytic processes, we introduce a streamlined workflow that separates the determination of photon flux from traditional actinometry experiments. Our method relies on radiometry to capture data regarding the light intensity of employed light sources. Leveraging this data, a light source model is formulated, which then facilitates the simulation of the maximal photon flux reaching the reaction mixture. This simulation employs ray-tracing, taking into account the reactor's material composition and geometric design. Armed with this insight, the experimental outcomes of chemical actinometry are repurposed to discern the effective optical path length rather than the photon flux. This pivot alleviates constraints on the absorbance in actinometry experiments, simplifying data collection by enabling exploration of extended irradiation durations or diminished concentrations. To showcase its efficacy, our method was validated on a non-intensified batch setup and subsequently applied to two distinct intensified flow reactors; a capillary reactor and a rotor-stator spinning disk reactor. Benchmark tests underscored the method's remarkable accuracy coupled with reduced effort post-model formulation. With the burgeoning interest in photocatalysis within industrial spheres, we posit that our approach is paramount for a nuanced comprehension of vital photochemical processes, paving the way for seamless scale-ups from lab to pilot and eventually, commercial levels. Additionally, our strategy offers a deeper dive into the energy balance of photochemical reactions, a crucial component for future operational expense (OPEX) analyses of the entire process. 17