Doppler Effect

Frequency shift for a moving source or observer

About this calculator

The Doppler Effect Calculator applies the classical formula f′ = f·(c + vₒ)/(c − vₛ) to find the frequency an observer hears when a source and/or observer move through a medium, using the toward-is-positive sign convention. It reports the observed frequency, the frequency shift and percentage change, the emitted and observed wavelengths, and the source's Mach number — and detects the breakdown cases where the source reaches the wave speed or the observer outruns the wave.

How to use the Doppler Effect calculator

  1. Enter the quantities you know, using the units shown on each field.
  2. Read the computed results — they update instantly as you type.
  3. Use the visual explanation to see how the quantities relate.
  4. Copy the page URL to share the exact calculation.

Common examples

  • 440 Hz source approaching at 30 m/s in air (c = 343 m/s) → observed ≈ 482.17 Hz, +9.58%
  • Same source receding at 30 m/s → observed ≈ 404.61 Hz, pitch lower
  • Observer approaching a stationary 700 Hz source at 20 m/s → hears ≈ 740.82 Hz
  • 1000 Hz siren approaching at 40 m/s → observed ≈ 1132.01 Hz, source at Mach 0.117

Frequently asked questions

How does the Doppler Effect calculator work?

Enter the known quantities and the calculator applies the governing physical law or scientific formula to find the unknowns, stating the equation it used and the units of every result. Computations run at high precision.

When would I use the Doppler Effect calculator?

It suits physics and chemistry homework, lab work, engineering estimates, and any time you want to explore how changing one quantity affects the others in a well-defined scientific relationship.

How accurate are the results?

The formula itself is evaluated at 30 significant digits of precision. Keep in mind that idealized models — such as neglecting friction, air resistance or measurement error — bound the real-world accuracy more than the arithmetic does.

Can I share a specific calculation with someone else?

Yes. Every value you enter updates the URL, so copying the address bar and sharing the link reopens the exact same calculation for whoever clicks it.