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Photon Energy Calculator

Convert a vacuum wavelength in nanometres to electromagnetic frequency and single-photon energy in joules and electronvolts.

Enter every field, including explicit zeros when permitted. Decimal and scientific notation are accepted; commas, fractions and blanks are rejected. Each input must be finite and no larger than 1 billion in absolute value. Observe the stated units and domain limits.

Frequency (Hz)545077196400000
Photon energy (J)3.61171974e-19
Photon energy (eV)2.254258153

How to use this calculator

  1. Enter every quantity in the unit printed beside its field.
  2. Select Calculate or press Enter.
  3. Read the labeled results and compare them with the assumptions below.

Formula and method

f = c/λ and E = hf, using exact SI values for c, h and the electronvolt conversion.

The calculation runs locally in your browser. If any entry is invalid or a mathematical condition is undefined, the prior result is hidden so it cannot be mistaken for a new answer.

Worked example

Using Wavelength (nm) = 550, the formula returns Frequency (Hz) = 545077196400000, Photon energy (J) = 3.61171974e-19, Photon energy (eV) = 2.254258153. The displayed default result is generated from these same inputs.

Limitations and safety

Uses vacuum wavelength. Wavelength inside a material differs because propagation speed changes. A photon’s energy does not by itself describe beam power or exposure risk. Results use floating-point arithmetic and are displayed to about 10 significant digits; measurement uncertainty usually supports fewer. Verify units before relying on a result.

Frequently asked questions

Does shorter wavelength mean more energy?

Yes. Photon energy is inversely proportional to wavelength, so decreasing wavelength raises energy per photon.

Why might a measured result differ?

The formula isolates the stated model. Real systems can add uncertainty, losses, changing properties, geometry or forces that are not among the inputs.

How should I handle units?

Convert every value to the unit shown beside its field before calculating. A numerically valid value in the wrong unit will still produce a wrong result.

Review notes and reference

Reviewed October 3, 2026. The default example and an independent edge or scaling case were checked against expected values. The live script was also checked for blank, text, comma-formatted, non-finite and out-of-range entries. Method reference. Constants use the values stated in the formula. This page’s explanation and example are original.

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