Phodominiant is an advanced scientific calculator designed to explore the boundary where light’s radiation pressure surpasses the thermal pressure of matter. By combining precision physics with an elegant gradient interface, the app allows researchers, engineers, and students to input temperature, number density, and surface reflectivity to determine the radiation-pressure-dominant regime. It supports both absorbing and reflecting models, handles scientific notation seamlessly (e.g., 1e20), and provides clear, formatted outputs in real physical units. With instant validation, one-tap calculation, copy/share functionality, and an informative guide explaining the underlying equations, Phodominiant transforms complex plasma and photonic pressure analysis into an intuitive, visually refined iOS experience making it an essential tool for anyone studying or engineering light–matter interactions.