Photon Energy Calculator
Calculate energy per photon from either wavelength or frequency using Planck's equation.
Results
What is “energy per photon”?
Light behaves as both a wave and a particle. The particle-like packet of light is called a photon. Each photon carries a discrete amount of energy, and that energy depends entirely on the photon’s frequency (or wavelength).
Higher frequency light (like ultraviolet, X-rays, and gamma rays) has more energy per photon. Lower frequency light (like radio waves and microwaves) has less energy per photon. This is why high-frequency radiation can trigger chemical changes more easily than low-frequency radiation.
Core formulas used in this calculator
From frequency
The direct relationship is:
E = hν
- E = energy per photon (J)
- h = Planck’s constant = 6.62607015 × 10-34 J·s
- ν (nu) = frequency (Hz)
From wavelength
Since frequency and wavelength are connected by c = λν, we also use:
E = hc / λ
- c = speed of light = 299,792,458 m/s
- λ (lambda) = wavelength (m)
How to use this calculator
- Select whether you want to calculate from wavelength or frequency.
- Enter a value and pick the correct unit (nm, µm, THz, GHz, etc.).
- Optionally enter a photon count for total energy.
- Click Calculate.
The calculator returns:
- Energy per photon in joules (J)
- Energy per photon in electronvolts (eV)
- Equivalent wavelength and frequency
- Total energy for your entered number of photons
- Energy per mole in kJ/mol
Worked examples
Example 1: Green laser light (532 nm)
A common green laser pointer emits around 532 nm light. Plugging that wavelength in gives an energy per photon in the visible-light range, around a few electronvolts. That’s enough to excite electrons in many fluorescent materials.
Example 2: Microwave oven frequency (2.45 GHz)
Microwaves are much lower frequency than visible light. A single microwave photon has much less energy than a visible photon. Heating in a microwave oven happens because of huge numbers of photons interacting with polar molecules, not because each photon is individually energetic.
Why use both joules and electronvolts?
Different fields prefer different units:
- Joules (J) are SI-standard and useful for engineering calculations.
- Electronvolts (eV) are convenient for atomic and quantum scale physics.
Converting between the two is straightforward: 1 eV = 1.602176634 × 10-19 J.
Common mistakes to avoid
- Mixing up wavelength units (nm vs µm vs m).
- Entering frequency in GHz but leaving unit at Hz.
- Using negative or zero values (physically invalid).
- Confusing energy per photon with total beam power.
Where this is useful
Photon energy calculations are useful in:
- Spectroscopy and optical labs
- Solar cell and LED analysis
- Photochemistry and fluorescence
- Astronomy and remote sensing
- Laser safety and instrumentation
Quick reference values
- 700 nm (red): lower visible photon energy
- 550 nm (green): mid-visible photon energy
- 400 nm (violet): higher visible photon energy
- 10 µm (infrared): lower than visible
- 100 MHz (radio): far lower than visible
If you work with wavelengths, frequencies, or spectroscopy data regularly, bookmark this page and reuse the calculator whenever you need fast, reliable photon energy conversions.