Wave Speed Calculator: v = f x wavelength

The wave equation for sound, light and water waves.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose which quantity you want to find.

Enter the other values in the units shown.

The calculator gives the answer with the formula, the substituted numbers, and the answer in other units.

Formulas used

  • v = f\,\lambda
  • f = \frac{v}{\lambda}
  • \lambda = \frac{v}{f}

Worked example

With the default numbers in the calculator above:

  1. The formula, arranged to find the wave speed: wave speed = frequency x wavelength
  2. Put the values in (every value in its SI unit): wave speed = 440 x 0.78
  3. The answer: wave speed: 343.2 m/s
  4. The same answer in other units: 1235.52 km/h

Change the numbers in the calculator to see the full working, every step, for your own case.

A second worked example

A different case, with these numbers: What do you want to find? Wavelength; Wave speed (leave it as it is if this is what you are finding) 343.2 m/s; Frequency (leave it as it is if this is what you are finding) 440 Hz.

  1. The formula, arranged to find the wavelength: wavelength = (wave speed) / (frequency)
  2. Put the values in (every value in its SI unit): wavelength = (343.2) / (440)
  3. The answer: wavelength: 0.78 m
  4. The same answer in other units: 78 cm; 780 mm; 7.8e+8 nm

Common questions

What is the wave equation?

Wave speed equals frequency times wavelength. A 440 Hz note in air with a wavelength of 0.78 m travels at 343 m/s.

How do I find the wavelength of light?

Divide the speed of light by the frequency. Green light at 5.5e14 Hz has a wavelength of about 545 nm.

Does the frequency change when a wave enters a new medium?

No. The frequency is fixed by the source. The speed and wavelength change.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any school physics text (waves).

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