🔆 Photon Energy Calculator (E = hf)
Find a photon’s energy from its frequency or wavelength (E = hf = hc/λ), shown in joules and eV.
Photon energy E
3.97289e-19 J (2.480e+0 eV)
Photon energy E = h·f = h·c/λ, with h = 6.626×10⁻³⁴ J·s, c = 3×10⁸ m/s. Result also shown in eV. 🔒 Computed in your browser.
How the photon energy calculator (e = hf) works
A photon’s energy is E = hf, where h is Planck’s constant (6.626×10⁻³⁴ J·s) and f the frequency; equivalently E = hc/λ. Enter a wavelength or frequency and the tool gives the energy in joules and electronvolts.
The joule↔eV conversion is a common stumbling point; the tool shows both. Shorter wavelength (higher frequency) means a more energetic photon — why UV damages skin but radio waves don’t.
Frequently asked questions
How do I calculate photon energy?
E = hf, or E = hc/λ from the wavelength. A 500 nm photon has E = hc/λ ≈ 3.97×10⁻¹⁹ J ≈ 2.48 eV. Enter frequency or wavelength.
What is Planck’s constant?
h = 6.62607015×10⁻³⁴ J·s (an exact defined value since 2019). It sets the energy of a photon per unit frequency.
How do I convert photon energy to eV?
Divide joules by the elementary charge (1.602×10⁻¹⁹). The tool shows the electronvolt value automatically.
Why do shorter wavelengths carry more energy?
Because E = hc/λ — energy is inversely proportional to wavelength. UV and X-rays (short λ) are far more energetic than visible or radio waves.
What is a photon?
A quantum (particle) of light. Its energy depends only on frequency (or wavelength), not intensity — brighter light means more photons, not more energetic ones.