Wavelength Converter Free Online
Convert between wavelength and frequency using c = 299,792,458 m/s (speed of light). Covers radio, microwave, infrared, visible light, UV, and X-rays. Shows electromagnetic spectrum band.
Pro — bulk batch conversion, API access, history & favorites
API access · Priority queue · Team workspace
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How It Works
Pick Your Unit or Preset
Choose your home unit using the dropdown or load a one-click preset. Defaults are sensible engineering values so you can start right away.
Enter a Value
Type a number — conversion runs as you type. Many tools have multiple input boxes (W & H, size & speed) — edit any of them and the rest recompute.
Read Every Equivalent
Below the main result, the All Units / Summary panel shows your value across every supported unit, with engineering context (FPS, ping, EM band, etc.) where relevant.
Wavelength Converter Features
c = 299,792,458 m/s
Uses the SI definition of the speed of light (exact). λ × ν = c. So 500 nm light = 600 THz.
Full Spectrum
Covers radio (km–m), microwave (mm), infrared (μm), visible light (380–750 nm), UV, X-ray, gamma. Shows the band label automatically.
Photon Energy
Auto-computes E = hν in eV. Visible light photons are ~1.8–3.3 eV; X-rays are 100 eV–100 keV.
Wavenumber
Spectroscopists' favorite — 1/λ in cm⁻¹. 500 nm = 20,000 cm⁻¹. Used in IR and Raman spectroscopy.
Bidirectional
Edit either wavelength or frequency — the other updates live, no swap needed.
100% Private
All math runs in your browser.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| Full wavelength conversion | ||
| Live conversion | ||
| All-units result panel | ||
| Bulk CSV / Excel conversion | — | |
| REST API access | — | |
| Custom precision settings | — |
Frequently Asked Questions
Visible light wavelength is 380–750 nm (violet to red). That corresponds to 400–790 THz. Green at 550 nm = 545 THz.
Wi-Fi 2.4 GHz = 12.5 cm wavelength. Wi-Fi 5 GHz = 6 cm. Wi-Fi 6E at 6 GHz = 5 cm. The shorter the wavelength, the more antennas can fit but the less penetration through walls.
FM 100 MHz = 3 m wavelength = 0.0000004 eV per photon. Green light 545 THz = 550 nm = 2.25 eV per photon. Visible light photons are 5+ million times more energetic than FM.
2.45 GHz = 12.2 cm wavelength. The cavity is sized so standing waves form, which is why food can have hot/cold spots — turn the plate or microwaves with a turntable to even it out.
1 / wavelength in cm. Spectroscopists prefer it because it is proportional to energy and frequency. 4000 cm⁻¹ ≈ 2.5 μm wavelength = 120 THz frequency, used in IR spectroscopy.