Diffraction Grating Calculator

About this calculator

This calculator applies the diffraction grating equation, mλ = d·sinθ, to find the angle at which light of wavelength λ constructively interferes after passing through a grating with line spacing d, for a given diffraction order m (m=1 being the first bright fringe off the central beam). Rearranged as θ = arcsin(mλ/d), it shows that closer-spaced lines (higher line density) or longer wavelengths bend light through a larger angle.

Physics students verifying spectroscopy lab results, optical engineers designing spectrometers or monochromators, and astronomers calibrating instruments that split starlight into spectra to identify chemical composition use this. Enter the wavelength, line density (or spacing), and diffraction order to get the diffraction angle.