Doppler Shift Calculator
Calculate the Doppler frequency shift on a radio signal caused by relative motion between transmitter and receiver, plus the resulting received frequency. Enter the carrier frequency and the closing (radial) velocity — positive when approaching, negative when receding.
Enter Values
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How to use this calculator
- Enter the carrier frequency f in MHz.
- Enter the relative radial velocity v in metres per second — positive if the source and receiver are closing on each other, negative if they are moving apart.
- Read the Doppler shift Δf in Hz and kHz and the shifted (received) frequency in MHz.
How it works
For speeds well below the speed of light the Doppler shift is Δf = f × v / c, where f is the carrier frequency, v is the radial (line-of-sight) velocity and c = 299,792,458 m/s. Approaching motion (positive v) adds to the frequency; receding motion (negative v) subtracts. The received frequency is simply f + Δf.
Worked example
Worked example. At f = 100 MHz (1×10⁸ Hz) with a closing speed v = 30 m/s: Δf = 1×10⁸ × 30 / 299,792,458 ≈ 10.007 Hz, so the received frequency is about 100.000010007 MHz.
Common mistakes
- Using the full ground speed instead of the radial component — only motion along the line of sight produces a first-order shift.
- Getting the sign wrong — approaching raises the frequency, receding lowers it.
- Applying this linear formula at speeds near the speed of light, where the relativistic Doppler formula is required.
Frequently asked questions
Does sideways motion cause a Doppler shift?
Not to first order. Only the radial (closing/opening) component of velocity shifts the frequency; motion purely across the line of sight gives no classical Doppler shift.
Is this the relativistic formula?
No. Δf = f·v/c is the non-relativistic approximation, which is accurate for radio, radar, aircraft and satellites. Near the speed of light you need the relativistic form with the √(1−v²/c²) factor.
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Tip: Enter any known values to calculate the remaining results.
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