How to use the photon energy calculator
Choose the input type, enter one positive value, and select Calculate. Wavelength is selected initially. Select the matching unit, then review Result and Formula & steps. The input accepts scientific notation such as 5e14.
- Select Wavelength or Frequency.
- Enter a positive value in Wavelength (λ) or Frequency (f).
- Choose Wavelength unit or Frequency unit.
- Select Calculate, then review Result and Formula & steps.
- Select Copy result or Download result (.txt). Select Reset to clear the form.
Calculate photon energy from wavelength or frequency
Wavelength values are converted to metres before the calculator uses E = h x c / lambda. Frequency values are converted to hertz before it uses E = h x f. The steps show h = 6.62607015 x 10^-34 J s and c = 299792458 m/s.
Input: Wavelength = 500 Nanometers (nm)
Output: Photon energy approx. 3.97 x 10^-19 JResult lists Photon energy, In eV, In meV, In keV, Frequency, and Wavelength. The text used by Copy result and Download result (.txt) also contains kJ/mol and kcal/mol.
Photon energy formula, units, and input limits
For Wavelength, the available choices are Meters (m), Centimeters (cm), Millimeters (mm), Micrometers (µm), Nanometers (nm), Picometers (pm), and Angstroms (Å). For Frequency, the choices are Hertz (Hz), Kilohertz (kHz), Megahertz (MHz), Gigahertz (GHz), Terahertz (THz), and Petahertz (PHz).
Enter one numeric value greater than zero. The entered number cannot exceed 1e30. A Wavelength value must also convert to at least 1e-30 m. Empty, negative, zero, nonnumeric, and non-finite input is rejected. The calculation uses the speed of light in a vacuum, so it does not adjust for air, glass, water, or another medium. Editing an input after calculation hides the previous result.
Where photon energy calculations come up
Choose Wavelength when the known value is a length. Choose Frequency when the known value is in hertz or a frequency multiple. The result includes both values, so you can check the conversion beside the energy.
For the example above, enter 500 Nanometers (nm) and select Copy result. If copying fails, select the generated text and copy it manually. Download result (.txt) creates photon-energy-calculator-result.txt.
When a different science calculator fits
Use Photon Energy Calculator when the known value is wavelength or frequency and the target is photon energy. Use Wavelength Calculator when the unknown is wavelength, frequency, or wave speed and any two of those values are known. Use Optics Calculator for thin-lens, mirror, magnification, optical-power, or wavelength-frequency calculations. Choose Kinetic Energy Calculator when the energy comes from mass and speed. Browse Science Calculators for other listed physics and chemistry calculations.
The calculation runs in the page. The calculator script does not send the entered value in a network request, while other page-level resources can load separately.
Frequently asked questions
What is the photon energy formula?
Use E = h x f for Frequency and E = h x c / lambda for Wavelength.
How do I calculate photon energy from wavelength?
Choose Wavelength, enter a positive value, select Wavelength unit, and select Calculate. The calculator converts the value to metres, then applies E = h x c / lambda.
How do I calculate photon energy from frequency?
Choose Frequency, enter a positive value, select Frequency unit, and select Calculate. The calculator converts the frequency to hertz, then applies E = h x f.
Can photon energy input be zero or negative?
No. Wavelength and frequency must be greater than zero. The calculator rejects zero or negative entries before calculating.
Does photon energy change with the medium in this calculator?
The calculator uses the speed of light in a vacuum, c = 299792458 m/s. It does not adjust the calculation for air, glass, water, or another medium.