What This Tool Does
Use this calculator to find the energy of a single photon from its wavelength or frequency. Enter one positive value, choose its unit, and select Calculate. Scientific notation such as 5e14 is accepted.
Choose an Input Mode and Unit
- Select Wavelength or Frequency.
- For wavelength, choose Meters (m), Centimeters (cm), Millimeters (mm), Micrometers (µm), Nanometers (nm), Picometers (pm), or Angstroms (Å).
- For frequency, choose Hertz (Hz), Kilohertz (kHz), Megahertz (MHz), Gigahertz (GHz), Terahertz (THz), or Petahertz (PHz).
The calculator normalizes wavelength to metres and frequency to hertz before calculating.
How to Calculate Photon Energy
- Select Wavelength or Frequency.
- Enter a positive numeric value and select its unit.
- Select Calculate to show the result and calculation steps.
- Select Copy result or Download result (.txt) to keep the output. Select Reset to clear the form.
How the Result Is Calculated
Wavelength input uses E = h × c / λ. Frequency input uses E = h × f. The calculation uses h = 6.62607015 × 10⁻³⁴ J·s and the vacuum speed of light, c = 299,792,458 m/s.
The visible result labels are Photon energy, In eV, In meV, In keV, Frequency, and Wavelength. The copied result and downloaded .txt file also include kJ/mol and kcal/mol.
Validation and Limitations
Inputs must be numeric, positive, finite, and no greater than the raw entered-value maximum of 1e30. Direct wavelength input must also convert to at least 1e-30 m. The calculator rejects non-finite frequency or photon-energy results.
That 1e-30 m check applies to directly entered wavelength, not to wavelength derived from frequency input. The calculation assumes light travels in a vacuum; it does not adjust for air, glass, water, or another medium, and it does not infer a missing input value.
Copying and Downloading Results
After a successful calculation, select Copy result to copy the generated text or Download result (.txt) to save it as photon-energy-calculator-result.txt. If copying fails, the tool displays “Could not copy - select and copy manually.” Because the generated result text is hidden, use Download result (.txt) as the available recovery option.
Privacy and Calculation Processing
The calculator code performs the unit conversion and photon-energy calculation locally in the page. The entered value is not sent by the calculator code itself. This page also loads analytics and other external resources, so this statement does not describe all page-level data handling.
Photon Energy Calculator FAQ
What is the formula for photon energy?
Photon energy equals Planck's constant times frequency: E = h × f. Since frequency and wavelength are related by f = c / λ, this can also be written E = h × c / λ, where c is the speed of light.
What units does this calculator support?
Wavelength can be entered using Meters (m), Centimeters (cm), Millimeters (mm), Micrometers (µm), Nanometers (nm), Picometers (pm), or Angstroms (Å). Frequency can be entered using Hertz (Hz), Kilohertz (kHz), Megahertz (MHz), Gigahertz (GHz), Terahertz (THz), or Petahertz (PHz). The visible result shows joules, electronvolts, millielectronvolts, and kiloelectronvolts; copied and downloaded text also includes kilojoules per mole and kilocalories per mole.
Why does photon energy increase as wavelength decreases?
Because energy is inversely proportional to wavelength (E = h × c / λ), shorter wavelengths carry more energy per photon. This is why ultraviolet, X-ray, and gamma-ray photons are more energetic than infrared or radio photons of longer wavelength.
Can wavelength or frequency be zero or negative in this calculator?
No. Wavelength and frequency must both be positive numbers greater than zero, since a photon with zero or negative wavelength or frequency has no physical meaning in this formula.
Does this calculator account for the medium the light travels through?
No. This calculator uses the speed of light in a vacuum (c = 299,792,458 m/s) for all wavelength-frequency conversions. It does not adjust for the refractive index of a medium such as glass or water.