Use the formula: wave speed = frequency × wavelength
Write it as: v = fλ
Measure the frequency in hertz (Hz)
Measure the wavelength in metres (m)
Multiply frequency by wavelength to get wave speed in metres per second (m/s)
If you know distance and time, use: wave speed = distance ÷ time
Write it as: v = d ÷ t
Rearrange the formula if needed:
frequency = wave speed ÷ wavelength
wavelength = wave speed ÷ frequency