Photon Energy Converter
Electron-volt
eV
Milli-electron-volt
meV
Kilo-electron-volt
keV
Mega-electron-volt
MeV
Giga-electron-volt
GeV
Joule
J
Erg
erg
Hartree
Eₕ
Hertz
Hz
Kilohertz
kHz
Megahertz
MHz
Gigahertz
GHz
Terahertz
THz
Petahertz
PHz
Meter
m
Centimeter
cm
Millimeter
mm
Micrometer (Micron)
µm
Nanometer
nm
Ångström
Å
Picometer
pm
Wavenumber
cm⁻¹
Kelvin (thermal kT)
K
Hover any row to copy or use as input.
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A precise photon energy converter built on exact 2019 SI constants (h = 6.62607015×10⁻³⁴ J·s, c = 299792458 m/s, k_B = 1.380649×10⁻²³ J/K). Converts across 23 units in four groups: Energy (eV, meV, keV, MeV, GeV, Joule, erg, Hartree), Frequency (Hz, kHz, MHz, GHz, THz, PHz), Wavelength (m, cm, mm, µm, nm, Å, pm), and Wave & Thermal (wavenumber cm⁻¹, Kelvin). Uses the Planck relation E = hf = hc/λ for frequency and wavelength conversions and Boltzmann thermal equivalence E = k_BT for Kelvin. Wavelength is correctly treated as inversely proportional to energy (E ∝ 1/λ). Essential for quantum mechanics, laser physics, spectroscopy, X-ray science, astrophysics, and physical chemistry. Defaults to 500 nm → eV (visible green light). Click any result row to use that value as a new input. 100% browser-based - no data leaves your device.
How to Use
- 1Type a photon energy value in the input field (must be positive)
- 2Select your starting unit from the From dropdown - choose from Energy (eV, J, Hartree…), Frequency (THz, GHz…), Wavelength (nm, Å, µm…), or Wave & Thermal (cm⁻¹, K)
- 3Select your target unit from the To dropdown - the result appears instantly
- 4All 23 conversions appear simultaneously, grouped by type: Energy, Frequency, Wavelength, and Wave & Thermal
- 5Hover any result row to reveal the copy and swap buttons
- 6Click the copy icon to copy a value to your clipboard
- 7Click the swap icon (⇅) on any row to use that unit as the new input and reverse the conversion
- 8Use the main swap button (⇄) in the input card to swap From and To units while preserving the physical photon energy
- 9Note that wavelength conversions are inverse - doubling the wavelength halves the energy, not doubles it
- 10Adjust 'Sig. figures' to control result precision (3 to 12 significant digits)
- 11Toggle 'Sci notation' for values that span many orders of magnitude (X-ray energies, radio wavelengths)
- 12Collapse a group by clicking its header to reduce clutter when you only need one domain
- 13Open 'Common conversions' at the bottom for a quick reference including visible light, X-ray, and thermal benchmarks
Features
- 23 photon energy units across 4 groups
- Energy: Electron-volt (eV), Milli-eV, Kilo-eV, Mega-eV, Giga-eV, Joule, Erg, Hartree
- Frequency: Hertz, Kilohertz, Megahertz, Gigahertz, Terahertz, Petahertz
- Wavelength: Meter, Centimeter, Millimeter, Micrometer, Nanometer, Ångström, Picometer
- Wave & Thermal: Wavenumber (cm⁻¹), Kelvin (thermal kT equivalent)
- Correct inverse handling of wavelength - E = hc/λ, not a simple linear factor
- All 23 conversions shown simultaneously - no need to select a single target unit
- Click any result row to use it as the new input for instant reverse conversion
- Adjustable significant figures: 3, 4, 5, 6, 8, 10, or 12 digits
- Toggleable scientific notation - essential for X-ray (keV, Å) and radio (MHz, cm) ranges
- Collapsible unit groups to reduce visual clutter
- One-click copy to clipboard for any converted value
- Built on exact 2019 SI-defined constants: h, c, k_B, and 1 eV - no rounding in constants
- 8-entry quick-reference table covering visible light, X-ray, THz, Hartree, and thermal benchmarks
- 100% browser-based - no server, no data upload
Frequently Asked Questions
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