Use the wave equation v = fλ to find wave speed, frequency or wavelength for sound, water or light, plus the period. In light mode it converts wavelength to frequency, gives the photon energy in joules and electronvolts and names the part of the electromagnetic spectrum.
Wave formulas
Worked examples
- Concert A (440 Hz) in air at 343 m/s has λ = 343 ÷ 440 = 0.78 m.
- Green light of 550 nm has f = 3.00 × 10⁸ ÷ 550 × 10⁻⁹ = 5.45 × 10¹⁴ Hz and each photon carries 2.25 eV.
- A 2.4 GHz Wi-Fi signal has a wavelength of 12.5 cm.
Frequently asked questions
How do I calculate wavelength?
Divide wave speed by frequency: λ = v / f. For light, use c = 3.00 × 10⁸ m/s.
How do I convert wavelength to frequency?
f = v / λ. For light, choose the light mode, enter the wavelength in nm and leave frequency empty.
How do I calculate photon energy?
E = hf or E = hc/λ, where h is Planck’s constant. The calculator gives the answer in joules and electronvolts.
What is the speed of sound?
About 343 m/s in air at 20 °C, roughly 1,480 m/s in water and around 5,000 m/s in steel.
Related tools
Free educational tool by HawkInc. Results are calculated in your browser and rounded for display; check critical work by hand or with a second method.