Wavelength to Energy Calculator

Created by Luciano Mino
Last updated: Nov 21, 2022

With our wavelength to energy calculator, you can easily find the amount of energy a photon carries by simply inputting the wavelength of its electromagnetic radiation.

In this short text, we will introduce you to the photon energy equation and its relation with its wavelength.

By the end, you will have learned how to calculate energy from wavelength and convert nm to eV in no time!

What are photons? Photon energy equation

Photons are particles of light. They have no mass, but they do have energy and momentum (see our photon energy calculator). The amount of energy a photon has is directly related to its wavelength.

By the energy-momentum relation, photons are relativistic particles since they travel at the speed of light.

💡 You can read more about these relativistic effects in our relativistic kinetic energy calculator.

Photon energy equation

The relationship between a photon's energy and its wavelength can be expressed by the following equation:

E=hcλE = \frac{hc}{\lambda}


  • EE is the energy of the photon (in joules).
  • hh is Planck's constant (6.62×1034 m2 kg/s6.62 \times 10^{-34} \ \text{m}^2\ \text{kg/s}).
  • cc is the speed of light in a vacuum (3.00×108 m/s3.00 \times 10^8 \ \text{m/s}).
  • λ\lambda is the wavelength of the photon (in meters). These are SI units, but you can input all these variables in any unit with our wavelength to energy calculator, including nm and eV.

How to convert between wavelength and energy of a photon

So, how do you calculate the energy from the wavelength of a photon? Use the equation above and input the wavelength of the photon's electromagnetic radiation. The result will be the energy the photon is carrying.

You can also easily switch from nm to eV with this wavelength to energy calculator. Simply select these units in the dropdown list next to each field.

If you want to convert energy to wavelength instead, you can either leave the wavelength field empty for our calculator to fill it for you (after inputting the photon's energy) or use the following formula:

λ=hcE\lambda = \frac{hc}{E}
Luciano Mino
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