Photon Momentum Calculator

About this calculator

This calculator finds a photon's momentum, p = h/λ, where h is Planck's constant and λ is the photon's wavelength, along with its energy, E = hc/λ (equivalently E = pc). Unlike massive particles, a photon's momentum comes entirely from its wave nature rather than from mv — a direct consequence of treating light as discrete quanta, as Einstein did to explain the photoelectric effect.

Physicists use this relationship throughout quantum mechanics and spectroscopy, where a photon's wavelength (color, in the visible range) directly tells you its energy and momentum. Photonics and optics engineers apply it when designing solar sails and studying radiation pressure — the tiny but real push light exerts on matter — and researchers use it when interpreting spectral lines from atoms or distant stars. Physics students studying wave-particle duality and quantum theory use this calculator to connect a photon's wavelength to its measurable physical properties.