Formulas

All inputs are converted to a common energy E (in joules); every output is then derived from E:

• Electronvolt: E = qe · (value in eV), so E[eV] = E / qe
• Frequency: E = h · ν, so ν = E / h
• Temperature: E = kB · T, so T = E / kB
• Photon wavelength: E = h c / λ, so λ = h c / E
• Rest energy ↔ mass: E = m c2, so m = E / c2
• Dark-matter de Broglie wavelength (interprets the input as the rest energy of a DM particle and uses the local galactic virial velocity v ≈ 220 km/s): λdB = h / (m v) = h c2 / (E v)

Constants (CODATA): h = 6.62607015 × 10-34 J·s, c = 2.99792458 × 108 m/s, kB = 1.380649 × 10-23 J/K, qe = 1.602176634 × 10-19 C.