Photon Energy Calculator
Energy of a photon from its wavelength, in electronvolts, attojoules and kilojoules per mole.
Results
Photon energy
2.25426
eV
Photon energy
0.361172
aJ
Frequency
545.0772
THz
Energy
217.503
kJ/mol
What this tool does
Visible light runs from about 380 nm at the violet end to 750 nm at the red, which is roughly 3.3 eV down to 1.65 eV. The energy per mole is the figure chemists use, because it says whether a photon carries enough to break a particular bond.
Formula
E = h c ÷ λ (h = 6,626 070 15 × 10⁻³⁴ J·s)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
wl | Wavelength | nm |
EV | Photon energy | eV |
EA | Photon energy | aJ |
F | Frequency | THz |
EM | Energy | kJ/mol |
Worked example
- Wavelength550 nm
- Photon energy2.25426 eV
- Photon energy0.361172 aJ
- Frequency545.0772 THz
- Energy217.503 kJ/mol
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.