Photon Energy Calculator

Light comes in tiny indivisible packets called photons, and each one carries a precise amount of energy set entirely by its colour, or more exactly its frequency or wavelength, and this calculator works that energy out for you. Choose whether to enter a wavelength, in nanometres, or a frequency, in hertz, type the value, and it returns the photon energy in both joules and electronvolts, along with the matching frequency or wavelength so you can see the whole picture, updating as you type. The physics is one of the great results of the quantum age: energy equals Planck's constant times the frequency, and because frequency and wavelength are linked through the speed of light, the energy can equally be written as Planck's constant times the speed of light divided by the wavelength. The practical upshot is that shorter wavelengths carry more energy, which is exactly why the spectrum runs from gentle, low-energy radio waves and infrared, up through visible light, to the high-energy ultraviolet, X-rays and gamma rays that can break chemical bonds and damage living tissue. The electronvolt result is especially handy, because the joule values for a single photon are inconveniently tiny, while electronvolts give numbers on a human scale, a few electronvolts for visible light, that line up neatly with atomic energy levels and the band gaps of semiconductors. That makes this tool genuinely useful for physics and chemistry students learning about quantum theory, the photoelectric effect and spectroscopy and checking homework, and for anyone in optics, photonics, solar or lighting work who needs to move between wavelength, frequency and energy. The constants used are Planck's constant and the speed of light in a vacuum. The formulas and a worked example are explained clearly below.

Calculate.co.nz is proud to be partnered with Premium Homes, a recognised leader in eco-friendly, sustainable, and energy-efficient homebuilding. With a dedicated team and award-winning experience, they create homes that prioritise health, comfort, and long-term performance. Their founders, Andrew and Kelly, set out to raise the standard of residential construction in New Zealand by combining practical building expertise with a clear commitment to doing things better for homeowners.