Photon Energy Calculator
Calculate photon energy from wavelength or frequency, in joules and electronvolts.
Please note: Results use idealised models — point masses, no air resistance, ideal gases and uniform materials. Real experiments deviate. Use these for study and estimation, not for engineering sign-off.
What the Photon Energy Calculator does
Light carries energy in discrete packets called photons, each with an energy set purely by its frequency through Planck’s constant. Because frequency and wavelength are inversely related, short-wavelength light carries far more energy per photon than long-wavelength light.
Formula
E = h × fE = h × c ÷ λp = h ÷ λ (photon momentum)h = 6.62607015 × 10⁻³⁴ J·s
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Specify the photon by | one of 3 options | Yes | — |
| Wavelength | number | In some modes | Shown Specify the photon by is Wavelength. |
| Wavelength unit | one of 9 options | In some modes | Shown Specify the photon by is Wavelength. |
| Frequency | number | In some modes | Shown Specify the photon by is Frequency. |
| Frequency unit | one of 5 options | In some modes | Shown Specify the photon by is Frequency. |
| Photon energy | number | In some modes | Shown Specify the photon by is Energy. |
| Photon energy unit | one of 8 options | In some modes | Shown Specify the photon by is Energy. |
| Number of photons | number | Optional | For the total energy of a pulse or beam. Accepts 0 or more. |
How to use it
- Choose Specify the photon by.
- Fill in the remaining inputs the form shows for your choice.
- Optionally add Number of photons.
- Select Calculate.
Worked example
A photon of green light at 550 nm.
- Wavelength
- 550 nm
f = c ÷ λ = 5.451 × 10¹⁴ Hz. E = hf = 3.612 × 10⁻¹⁹ J, which is 2.254 eV.
Frequently asked questions
Why is ultraviolet light harmful when visible light is not?
UV photons carry over 3 eV each, enough to break chemical bonds in DNA. Visible photons fall short of that threshold no matter how bright the light is.
What is an electronvolt?
The energy an electron gains moving through one volt: 1.602 × 10⁻¹⁹ J. It keeps photon and particle energies at readable magnitudes.