Science & Engineering

Photon Energy Calculator

Computes photon energy from wavelength using E = hc / lambda, reporting the result in both joules and electronvolts, with wavelength entered in nanometres.

What this calculator does

The Photon Energy Calculator estimates your result instantly from the values you enter, using standard science & engineering formulas. Computes photon energy from wavelength using E = hc / lambda, reporting the result in both joules and electronvolts, with wavelength entered in nanometres. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.

Photon Energy Calculator

Result

—
Energy (J)
—
Energy (eV)

About Photon Energy Calculator

This photon energy calculator applies E = hc/λ, using Planck's constant h = 6.62607015×10−34 J·s and the speed of light c = 2.99792458×108 m/s. Enter a wavelength in nanometres and it returns the photon energy in both joules (J) and electronvolts (eV).

The nanometre input is converted to metres, and the joule result is divided by 1.602176634×10−19 to express the energy in eV.

Formula & Mathematical Calculation

Energy (J) = f(Wavelength (nm))

Calculated according to standard science formulas implemented in the calculator core.

Calculation Example

For a wavelength of 500 nm, E = hc/λ = (6.62607015×10−34 × 2.99792458×108) / (500×10−9) = 3.9729×10−19 J, which is about 2.4797 eV.

Key Benefits

  • Applies E = hc over lambda with the exact CODATA values for h and c
  • Reports energy in both joules and electronvolts
  • Accepts wavelength in nanometres and converts to metres internally
  • Shows the joule result in scientific notation for very small energies

How to Use this Calculator

  1. Enter the wavelength
    Type the photon's wavelength in nanometres in the Wavelength (nm) field.
  2. Calculate
    Press Calculate to compute the photon energy.
  3. Read both energy values
    Read the energy in joules and in electronvolts from the two result boxes.

Assumptions & Limitations

What the calculation assumes

  • Every value you enter is treated as an exact, known amount.
  • Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
  • Results use standard published formulas and account only for the values entered above.
  • Rounding is applied for display; the underlying calculation uses your full precision.
  • Results are returned in the same units you enter, unless the tool states the output unit.

What it does not cover

  • Photon Energy Calculator produces a calculated result for reference and learning, not a certified or official measurement.
  • Real-world outcomes differ when tolerances, rounding rules or local standards apply.
  • Definitions and standards vary by region and change over time; verify the convention that applies to your case.
  • Figures are only as accurate as the inputs you supply — check them before acting on the result.
  • For work where the result carries real consequences, confirm it against an authoritative source.

Frequently Asked Questions

It uses E = hc divided by wavelength, with Planck's constant h = 6.62607015e-34 J s and the speed of light c = 2.99792458e8 m/s.

Enter the wavelength in nanometres. The calculator converts it to metres by multiplying by 1e-9 before computing the energy.

The joule result is divided by 1.602176634e-19, the number of joules in one electronvolt, to give the energy in eV.

Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.