de Broglie Wavelength Calculator

About this calculator

Louis de Broglie proposed in 1924 that every moving particle has an associated matter wave, with wavelength given by λ = h / p, where h is Planck's constant (6.626×10⁻³⁴ J·s) and p is momentum (mass × velocity for non-relativistic speeds). This single equation unified the wave and particle descriptions of matter and underlies why electrons, despite being particles, produce diffraction patterns just like light.

This calculator takes a particle's mass and velocity, computes its momentum, and returns its de Broglie wavelength. Physics students use it to build intuition for why macroscopic objects (a thrown ball) have imperceptibly tiny wavelengths while electrons and other subatomic particles have wavelengths comparable to atomic spacing — the principle that makes electron microscopy and electron diffraction possible.