De Broglie Wavelength Calculator

Divide the Planck constant by the particle's momentum: λ = h / (m × v), with h = 6.62607015e-34 J·s. Use kilograms and metres per second, and the wavelength comes out in metres. An electron of 9.1093837e-31 kg at 10000000 m/s reaches about 0.0727 nm.

It is the wavelength attached to a moving particle. Louis de Broglie proposed in 1924 that all matter has wave-like properties, with a wavelength equal to the Planck constant divided by the particle's momentum. It is the foundation of wave-particle duality.

Because their momentum is enormous next to the tiny Planck constant. A thrown ball comes out around 1e-34 m, far smaller than an atom, so its wave nature is undetectable. Matter waves only become measurable for very light, fast particles such as electrons.

Not accurately. This calculator uses the classical momentum m × v, which is fine well below light speed — at 10000000 m/s the error stays under a tenth of a percent. Close to c you need the relativistic momentum, which makes the wavelength shorter than the simple formula predicts.

No — the de Broglie wavelength is defined for particles with mass. Photons have no rest mass, so their wavelength follows from their energy instead. Use this calculator for electrons, protons, neutrons, atoms and other massive particles.

Because in metres every realistic answer would read as 0.000000 — matter wavelengths sit between 1e-12 and 1e-9 m, and the readout carries six decimals. One nanometre is 1e-9 m, so 0.072739 nm is 7.2739e-11 m. Atomic distances live in exactly this range, which is what makes the number readable.