SpectralBench
Instant conversion between spectroscopic units
Spectroscopists routinely switch between wavenumber, wavelength, frequency, and energy representations depending on the technique, the journal, or the audience. Getting the conversion right matters — especially when comparing results across UV-Vis, IR, and Raman measurements that each favor different units.
The SpectralBench unit converter handles all common spectroscopic units in one place. Enter a value in any field and every other unit updates instantly. Calculations use NIST-recommended physical constants so you can trust the results in publications and reports. Need to convert peak positions from an FTIR measurement? Load your spectrum in the Spectral File Viewer and use the converter alongside it.
Enter a value in any of the eight unit fields — wavenumber (cm⁻¹), wavelength (nm), wavelength (μm), frequency (Hz), frequency (THz), energy (eV), energy (kJ/mol), or energy (J). All other fields update in real time with the converted values. The conversion is bidirectional: change any field and the rest recalculate instantly.
SpectralBench uses NIST 2018 CODATA recommended values for physical constants including the speed of light, Planck's constant, and the elementary charge. This ensures your converted values are accurate enough for publication-quality work and consistent with international measurement standards.
The relationships between spectroscopic units are derived from the fundamental equation E = hν = hc/λ = hcν̃, where h is Planck's constant, c is the speed of light, λ is wavelength, ν is frequency, and ν̃ is wavenumber.
Wavenumber → Wavelength: λ(nm) = 10⁷ / ν̃(cm⁻¹)
Wavenumber → Frequency: f(Hz) = ν̃(cm⁻¹) × c, where c = 2.998 × 10¹⁰ cm/s
Wavenumber → Energy: E(eV) = ν̃(cm⁻¹) × 1.2398 × 10⁻⁴
Wavelength → Frequency: f = c / λ
SpectralBench uses NIST 2018 CODATA recommended values for all physical constants, so conversions match the precision expected in analytical chemistry and physics publications.
Enter a wavenumber value in cm⁻¹ into SpectralBench and the wavelength in nanometers updates instantly. The formula is λ(nm) = 10⁷ / ν̃(cm⁻¹). For example, 1000 cm⁻¹ equals 10,000 nm (10 μm).
Wavenumber (cm⁻¹) and wavelength (nm) are reciprocally related: a higher wavenumber corresponds to a shorter wavelength and higher energy. The conversion is λ(nm) = 10⁷ / ν̃(cm⁻¹). This inverse relationship means equal steps in wavenumber do not correspond to equal steps in wavelength.
Wavenumber is directly proportional to energy and frequency, making it the natural unit for infrared and Raman spectroscopy. Equal spacing in wavenumber corresponds to equal spacing in energy, which simplifies spectral interpretation, peak comparison, and thermodynamic calculations.
1000 cm⁻¹ equals 10,000 nm, which is 10 μm. This falls in the mid-infrared region of the electromagnetic spectrum, where many molecular vibrations (C-O, C-N, and fingerprint region absorptions) are observed.