Doppler Effect Calculator
Observed frequency for a moving source.
Enter your values
Enter the source frequency in Hz.
Enter the source speed in m/s.
Enter the observer speed in m/s.
Enter the speed of sound in m/s.
Choose one of: Source approaching, Source receding.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Observed frequency
- 467.24 Hz
- Frequency shift
- 27.24 Hz
- Percentage shift
- 6.19%
- Semitones shift
- 1.04
Quick answer
The Doppler effect raises observed frequency when a source approaches and lowers it as it recedes.
f' = f(v ± vo) ÷ (v ∓ vs)
At a glance
| What it does | Observed frequency for a moving source. |
|---|---|
| Category | Science |
| Inputs needed | Source frequency, Source speed, Observer speed, Speed of sound, Motion |
| Main output | Observed frequency |
| Formula | f' = f(v ± vo) ÷ (v ∓ vs) |
| Cost | Free — no sign-up, no download |
How to use the Doppler Effect Calculator
- 1Enter the source's true frequency.
- 2Enter source and observer speeds.
- 3Choose whether the source approaches or recedes.
Inputs explained
- Source frequency(Hz)
- Enter the source frequency in Hz.
- Source speed(m/s)
- Enter the source speed in m/s.
- Observer speed(m/s)
- Enter the observer speed in m/s.
- Speed of sound(m/s)
- Enter the speed of sound in m/s.
- Motion
- Choose one of: Source approaching, Source receding.
Worked example
Using the values the calculator loads with:
Inputs
- Source frequency440 Hz
- Source speed20 m/s
- Observer speed0 m/s
- Speed of sound343 m/s
- MotionSource approaching
Results
- Observed frequency467.24 Hz
- Frequency shift27.24 Hz
- Percentage shift6.19%
- Semitones shift1.04
Frequently asked questions
Why does a siren drop in pitch?
As it passes, the source switches from approaching to receding.
Does light Doppler shift too?
Yes — that is redshift, though it needs relativistic formulas.
What do I need to enter into the Doppler Effect Calculator?
Just 5 values: source frequency, source speed, observer speed, speed of sound, motion. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Doppler Effect Calculator work out the answer?
The Doppler effect raises observed frequency when a source approaches and lowers it as it recedes. It applies the formula f' = f(v ± vo) ÷ (v ∓ vs) and shows the working so you can check each step by hand.
Is the Doppler Effect Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.