Doppler Effect Calculator (Frequency Shift)

The Doppler effect is the change in frequency of a wave relative to an observer moving relative to the source.

Classical formula:
f' = f · (v ± vo) / (v ∓ vs)

Sign convention:

• +vo when observer approaches; −vo when receding.
• −vs when source approaches; +vs when receding.

Derived: Δf = f' − f, wavelength ahead = (v − vs)/f, behind = (v + vs)/f.

Classical formula (sound). For light at relativistic speeds use the relativistic formula. If v_s ≥ v, a shock wave forms.