Wavelength & Frequency Calculator (c = fλ)
Calculate wavelength, frequency and photon energy of light using c = fλ. Enter wavelength in metres or frequency in Hz to find the other.
How to use this tool
- Enter wavelength (λ) and frequency (f) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your frequency and the full breakdown beneath it.
The speed of light is c = f × λ = 299,792,458 m/s. Given either wavelength λ (metres) or frequency f (Hz), the other follows directly. Photon energy is E = hf where h = 6.626 × 10⁻³⁴ J·s.
Frequently asked questions
- What wavelength is visible light?
- Visible light spans roughly 380 nm (violet) to 700 nm (red). Green is around 550 nm with frequency ~545 THz.
- Why is the speed of light fixed?
- In vacuum, c is a fundamental constant (≈ 3 × 10⁸ m/s) by definition since 1983. In other media light slows down by a factor of the refractive index.