Enter the Systolic Velocity, Diastolic Velocity, and Mean Velocity into the Pulsatility Index Calculator to determine the Pulsatility Index; this calculator can also evaluate any of the variables given the others are known.

Pulsatility Index Formula

The following formula is used to calculate the Pulsatility Index (PI) in a Pulsatility Index Calculator:

 PI = (Systolic V - Diastolic V) / Mean V


  • PI is the Pulsatility Index
  • Systolic Velocity is the maximum velocity of blood flow during systole
  • Diastolic Velocity is the minimum velocity of blood flow during diastole
  • Mean Velocity is the average velocity of blood flow over a cardiac cycle

To calculate the Pulsatility Index, subtract the Diastolic Velocity from the Systolic Velocity, and then divide the result by the Mean Velocity.

What is a Pulsatility Index?

The Pulsatility Index (PI) is a measure used in Doppler ultrasound studies to quantify the variability in blood flow velocity within a specific blood vessel. It is calculated by subtracting the diastolic velocity (the speed of blood flow when the heart is at rest) from the systolic velocity (the speed of blood flow when the heart is contracting), and then dividing the result by the mean velocity (the average speed of blood flow throughout the entire cardiac cycle). The PI provides information about the resistance to blood flow caused by changes in the blood vessel, such as narrowing or blockage. A higher PI indicates greater variability in blood flow velocity, which may suggest increased resistance or decreased compliance of the blood vessel. This can be indicative of various pathological conditions, such as vascular disease or fetal distress in obstetric applications.

How to Calculate Pulsatility Index?

The following steps outline how to calculate the Pulsatility Index:

  1. First, determine the systolic velocity (SV) in cm/s.
  2. Next, determine the diastolic velocity (DV) in cm/s.
  3. Next, determine the mean velocity (MV) in cm/s.
  4. Use the formula PI = (SV – DV) / MV to calculate the Pulsatility Index.
  5. Finally, calculate the Pulsatility Index using the given values.

Example Problem:

Use the following variables as an example problem to test your knowledge:

Systolic velocity (SV) = 120 cm/s

Diastolic velocity (DV) = 80 cm/s

Mean velocity (MV) = 100 cm/s