🔬 Compton Scattering Calculator
Calculate how much a photon’s wavelength shifts after scattering off a free electron, based on the scattering angle (the Compton effect).
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What Compton scattering is
Compton scattering occurs when a photon (such as an X-ray) collides with a nearly-free electron, transferring some energy to the electron and increasing the photon’s wavelength (reducing its energy). The size of the shift depends only on the scattering angle.
The formula
The Compton scattering formula is Δλ = (h / (me·c))(1 – cosθ), where h is Planck’s constant, me is the electron rest mass, c is the speed of light, and θ is the scattering angle. The term h/(me·c) is called the Compton wavelength of the electron, about 2.426 picometers.
This calculator is for general physics education and reference.
Last reviewed August 2026