Photon Energy (E = hf) Calculator
Find the energy carried by a single photon from its frequency or wavelength, reported in both joules and electronvolts.
Input mode
nm
3.9729e-19 joules
- 1
Wavelength in metres
500 nm × 10⁻⁹ = 5.0000e-7 m - 2
Frequency f = c ÷ λ
2.998×10⁸ ÷ 5.0000e-7 = 5.9958e+14 Hz - 3
Energy E = h × f
6.626×10⁻³⁴ × 5.9958e+14 = 3.9729e-19 J - 4
Energy in eV
3.9729e-19 ÷ 1.602×10⁻¹⁹ = 2.4797
How does this calculator work?
A photon’s energy equals Planck’s constant times its frequency, E = h·f, or equivalently h·c/λ. Enter the frequency in hertz or the wavelength in nanometres, and the calculator returns the photon energy in both joules and electronvolts, plus the complementary frequency or wavelength on the electromagnetic spectrum.
Formula
How this is calculated
A photon's energy is set entirely by its frequency through the Planck relation E = h·f, where h = 6.62607015×10⁻³⁴ J·s is the Planck constant. If you instead know the wavelength λ, frequency follows from the wave relation f = c/λ (c = 2.99792458×10⁸ m/s), giving the equivalent form E = h·c/λ. Shorter wavelengths therefore mean higher frequency and more energetic photons.
Select the input mode to enter either the frequency f in hertz or the wavelength λ in nanometres. Wavelengths are converted to metres (1 nm = 10⁻⁹ m) before the calculation. The result is given in joules and converted to electronvolts by dividing by the elementary charge in joules, 1.602176634×10⁻¹⁹, since 1 eV is the energy gained by an electron moving through a one-volt potential difference.
Inputs must be positive and finite; zero or negative values are rejected because they have no physical meaning here. The RangeMeter places the wavelength on a 100 nm–1 mm electromagnetic-spectrum scale spanning ultraviolet, visible, and infrared light. Results assume a photon travelling in vacuum.
Frequently asked questions
Visible wavelengths (about 400–700 nm) correspond to frequencies near 4–7×10¹⁴ Hz, which through E = h·f works out to roughly 1.8–3.1 eV per photon — small in joules but enough to drive many chemical and biological processes.
Divide the energy in joules by 1.602176634×10⁻¹⁹ J/eV. The calculator reports both values automatically so you do not need to convert by hand.
The energy depends on frequency, which is unchanged when light enters a medium. Wavelength does change with refractive index, so this calculator assumes vacuum where λ = c/f.
Also known as
TG we-Calculate Editorial Team. (2026). Photon Energy (E = hf) Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/photon-energy-calculator
TG we-Calculate Editorial Team. "Photon Energy (E = hf) Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/photon-energy-calculator.
TG we-Calculate Editorial Team, "Photon Energy (E = hf) Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/photon-energy-calculator
@misc{wecalculate_photon_energy_calculator, title = {Photon Energy (E = hf) Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/photon-energy-calculator}}, year = {2026}, note = {TG we-Calculate} }
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