Doppler equation calculator
Explore doppler equation with the method’s inputs, acquisition guidance and source references. Open the calculator to enter measurements or try an illustrative worked example.
Method
Δf = 2fₜv cosθ/c; v = |Δf|c/(2fₜ cosθ)
Use the measurement units shown below. Some fields apply only to a selected method or condition; follow the interactive tool’s method choices. The interactive tool keeps missing measurements incomplete and provides its method-specific results and reference context.
Measurements and acquisition
Solve for
Enter the measured value in the displayed unit
- Velocity
- Frequency shift
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.
Shift magnitude · |Δf| kHz
Enter the measured value in the displayed unit
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.
Blood speed · v m/s
Enter the measured value in the displayed unit
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.
Transmit frequency · fₜ MHz
Enter the measured value in the displayed unit
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.
Beam-to-flow angle · θ °
Enter the measured value in the displayed unit
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.
Sound speed · c m/s
Enter the measured value in the displayed unit
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.
Sources and method context
ASE · 2019 · Doppler equation and cardiac spectral acquisition · ASE Comprehensive TTE · spectral Doppler, p. 42; Manual of Neurosonology (2016), Fig. 1.5
- Alignment in echocardiography · ASE Comprehensive TTE (2019), p. 42
Detected velocity depends on cosine of the beam-to-flow angle. Improve alignment and compare windows rather than using angle correction; choose a well-acquired maximum-velocity signal.
- Equation and sign · Cambridge, Manual of Neurosonology (2016), pp. 4–5, Fig. 1.5
Frequency shift is proportional to transmitted frequency, flow speed and cosine of the angle. Perpendicular flow has zero axial shift.
- Two Doppler interactions · OpenStax College Physics 2e §17.7, Doppler-shifted ultrasound and Example 17.8
A moving scatterer first receives sound and then acts as a moving source. In the low-speed approximation each contributes half of the total echo shift.
Catalogue review status: Source mapped · clinical sign-off pending
These pages describe the educational tool. Interpret measurements with the complete clinical context and the method’s acquisition limitations.