Doppler Ultrasound Calculator
A 5 MHz beam aligned with blood moving at 20 cm/s returns a Doppler shift of 1298.7 Hz, conveniently in the audible range.
1298.7012987013 Hz
Full answer, then cut to fewer decimals (not rounded):
- 1298.7012987013 Hz
- 1298.701298701 Hz
- 1298.70129870 Hz
- 1298.7012987 Hz
- 1298.701298 Hz
- 1298.70129 Hz
- 1298.7012 Hz
- 1298.701 Hz
- 1298.70 Hz
- 1298.7 Hz
- In kHz
- 1.298701299 kHz
Step-by-step solution
- Convert units: f₀ = 5 MHz = 5000000 Hz; v = 20 cm/s = 0.2 m/s
- Δf = 2 × f₀ × v × cos θ° ÷ c
- Δf = 2 × 5000000 × 0.2 × cos 0° ÷ 1540
- Δf = 1298.701299 Hz
Doppler Ultrasound Formula
Δf = 2 f₀ v cos θ / c
c ≈ 1540 m/s in soft tissue; θ the angle between beam and flow
Worked Example
A 5 MHz probe aligned with blood moving at 20 cm/s:
- Convert units: f₀ = 5 MHz = 5000000 Hz; v = 20 cm/s = 0.2 m/s
- Δf = 2 × f₀ × v × cos θ° ÷ c
- Δf = 2 × 5000000 × 0.2 × cos 0° ÷ 1540
- Δf = 1298.701299 Hz
GATE tip
Pulsed Doppler aliases when Δf exceeds half the pulse repetition frequency. The maximum measurable velocity is v_max = c × PRF/(4f₀ cos θ).
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Frequently asked questions
Why the factor 2?
The moving blood first receives a shifted frequency and then re-emits it as a moving source, so the shift doubles.
Why keep the angle below 60°?
cos θ changes quickly near 90°, so small angle errors cause large velocity errors; at 90° there is no shift at all.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Doppler Ultrasound Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/doppler-ultrasound-calculator/
IEEE
Scientific Converters, "Doppler Ultrasound Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/doppler-ultrasound-calculator/