Doppler Effect Calculator
Find the frequency a listener actually hears when a sound source and/or the observer are moving relative to the medium.
Hz
m/s
m/s
Observer motion
m/s
Source motion
Pitch rises (frequency increases)
- 1
Numerator (v ± vo)
343 + 20 = 363Observer moves toward source — adds to numerator (higher pitch). - 2
Denominator (v ∓ vs)
343 − 30 = 313Source moves toward observer — subtracts from denominator (higher pitch). - 3
Frequency ratio
363 ÷ 313 = 1.1597 - 4
Observed frequency f'
440 × 1.1597 = 510.29
How does this calculator work?
The observed frequency is f' = f·(v ± vo)/(v ∓ vs), where v is the wave speed, vo the observer speed, and vs the source speed. Use the upper signs when motion is toward, lower when away. Motion toward raises the pitch; motion away lowers it. The shift is Δf = f′ − f.
Formula
How this is calculated
The Doppler effect changes the frequency perceived by an observer when there is relative motion between a sound source and the observer through the carrying medium (air). Enter the true source frequency f (Hz), the wave speed v in the medium (default 343 m/s for air at 20°C), the observer speed vo, and the source speed vs (both in m/s). Two selectors set whether the observer and source are moving toward or away from each other.
The relation is f' = f·(v ± vo)/(v ∓ vs). The numerator uses +vo when the observer moves toward the source (higher pitch) and −vo when moving away. The denominator uses −vs when the source moves toward the observer (higher pitch) and +vs when moving away. The frequency shift is Δf = f′ − f, and the percent shift is 100·Δf/f.
This classical formula assumes speeds are measured relative to a stationary medium and that the source speed is below the wave speed (vs < v); at or above v the denominator reaches zero or goes negative (shock-wave / Mach regime) and the simple formula no longer applies. It does not include relativistic corrections, which matter only for light or speeds near c.
Frequently asked questions
As the source moves toward you the wavefronts bunch up, shortening the wavelength and raising the frequency you hear. After it passes, the wavefronts stretch out and the pitch drops.
For sound in air near 20°C use about 343 m/s. Sound is faster in warmer air, and much faster in water (~1480 m/s) or steel (~5000 m/s). Use the medium-appropriate value.
This is the classical acoustic Doppler formula. For light you need the relativistic Doppler equation, since there is no medium and time dilation matters at high speeds.
Also known as
TG we-Calculate Editorial Team. (2026). Doppler Effect Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/doppler-effect-calculator
TG we-Calculate Editorial Team. "Doppler Effect Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/doppler-effect-calculator.
TG we-Calculate Editorial Team, "Doppler Effect Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/doppler-effect-calculator
@misc{wecalculate_doppler_effect_calculator, title = {Doppler Effect Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/doppler-effect-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?