Medical Equations

Stroke Volume Calculator

Stroke Volume equals End Diastolic Volume minus End Systolic Volume

Solution

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Worked Examples

Normal Systolic Function

Calculate SV and EF from EDV 120 mL and ESV 50 mL

This common echo-style example produces a normal ejection fraction and a typical resting stroke volume.

  1. Choose Solve for Stroke Volume.
  2. Enter 120 for EDV and 50 for ESV.
  3. Read the stroke volume of 70 mL.
  4. Notice that the calculator also reports an ejection fraction of about 58.3%.
  5. Use the paired SV and EF values together when summarizing ventricular systolic function.

Having both SV and EF on the same screen makes it easier to sanity-check the hemodynamic interpretation.

Reduced EF Example

Spot reduced systolic function from EDV 150 mL and ESV 100 mL

A larger ventricle with a high residual volume can still eject a modest amount of blood but have a poor fraction of emptying.

  1. Choose Solve for Stroke Volume.
  2. Enter 150 for EDV and 100 for ESV.
  3. Read the stroke volume of 50 mL.
  4. Check the ejection fraction of about 33.3%, which is well below normal.
  5. Use the low EF as a prompt to think about systolic heart failure or major contractile impairment.

This demonstrates why stroke volume alone does not fully describe ventricular performance.

Reverse Solve

Find EDV when SV is 75 mL and ESV is 45 mL

Reverse solving is helpful when you know the blood ejected per beat and the residual volume but want the pre-contraction filling volume.

  1. Choose Solve for End Diastolic Volume.
  2. Enter 75 for stroke volume and 45 for ESV.
  3. Read the end-diastolic volume of 120 mL.
  4. Confirm the result by checking that 120 - 45 returns the original 75 mL stroke volume.
  5. Use the completed volume set to discuss preload and ventricular size more clearly.

This is useful in teaching settings where you want to move smoothly between the three variables in the equation.

Solve for Stroke Volume

Calculate stroke volume by subtracting end-systolic volume from end-diastolic volume. A typical resting SV for a healthy adult is 60 to 80 mL.

SV = EDV − ESV

Solve for End Diastolic Volume

Determine the end-diastolic volume from stroke volume and end-systolic volume. EDV reflects the total ventricular filling.

EDV = SV + ESV

Solve for End Systolic Volume

Calculate the residual volume remaining in the ventricle after contraction. ESV reflects the completeness of ventricular emptying.

ESV = EDV − SV

How It Works

Stroke volume (SV) is the volume of blood ejected from the left ventricle with each heartbeat. It is calculated as the difference between the end-diastolic volume (the volume of blood in the ventricle at the end of filling) and the end-systolic volume (the volume remaining after contraction). The calculator also automatically computes ejection fraction (EF = SV / EDV × 100) when all three volumes are known.

Example Problem

An echocardiogram reports an end-diastolic volume (EDV) of 120 mL and an end-systolic volume (ESV) of 50 mL.

  1. Select the stroke volume form because EDV and ESV are the known measurements.
  2. Subtract the end-systolic volume from the end-diastolic volume: 120 - 50 = 70 mL.
  3. Read the stroke volume result of 70 mL.
  4. Use the same numbers to estimate ejection fraction: 70 / 120 × 100 = 58.3%.
  5. Compare the EF with the usual normal range of about 55% to 70% to support the systolic assessment.

Stroke volume is only one part of the hemodynamic picture, so ventricular filling, afterload, and valvular disease still matter.

Formula Guide

These variables describe how much blood the ventricle holds before contraction, how much remains afterward, and how much is actually ejected.

EDV = End Diastolic Volume (mL)

The ventricular volume at the end of filling, just before systole begins.

ESV = End Systolic Volume (mL)

The ventricular volume remaining after contraction.

SV = Stroke Volume (mL)

The amount of blood ejected with each heartbeat, calculated as EDV minus ESV.

EF = Ejection Fraction (%)

The proportion of EDV ejected each beat, useful for interpreting systolic function.

When to Use Each Variable

  • Solve for SV — when you have EDV and ESV from echocardiography and need to calculate the blood volume ejected per beat.
  • Solve for EDV — when SV and ESV are known and you need to determine the total ventricular filling volume.
  • Solve for ESV — when EDV and SV are known and you need to find the residual volume after contraction.

Key Concepts

The ejection fraction (EF) represents the percentage of blood ejected from the left ventricle with each contraction. A normal EF is typically 55 to 70%. Values below 40% indicate systolic heart failure (HFrEF), while preserved ejection fraction heart failure (HFpEF) involves an EF above 50% but with diastolic dysfunction. Three main factors govern SV: preload (Frank-Starling mechanism), afterload (aortic resistance), and contractility (myocardial force generation).

Applications

  • Echocardiographic assessment of ventricular function
  • Calculating cardiac output (CO = SV × HR)
  • Heart failure classification (HFrEF vs. HFpEF)
  • Monitoring response to inotropic therapy
  • Pre- and post-operative cardiac evaluation

Common Mistakes

  • Confusing stroke volume (mL/beat) with cardiac output (L/min)
  • Using indexed values (SVI) without dividing by BSA
  • Not recognizing that normal SV ranges vary with body size and sex
  • Interpreting EF in isolation without considering diastolic function

Frequently Asked Questions

How is stroke volume measured?

Echocardiography is the primary noninvasive method for measuring stroke volume. The Simpson biplane method estimates ventricular volumes by tracing the endocardial border at end-diastole and end-systole. Doppler echocardiography can also calculate SV from the left ventricular outflow tract diameter and velocity-time integral.

What factors affect stroke volume?

Three main factors govern SV: preload (Frank-Starling mechanism), afterload (aortic resistance), and contractility (myocardial force generation). Increasing preload or contractility raises SV, while increased afterload tends to decrease it.

What is a normal end-diastolic volume?

Normal left ventricular end-diastolic volume is approximately 110 to 120 mL in adult males and 90 to 100 mL in adult females. Values above these ranges may indicate volume overload or dilated cardiomyopathy.

Why does the calculator also show ejection fraction?

Ejection fraction gives context for how efficiently the ventricle empties. A patient can have a modest stroke volume but still a normal EF, or a similar stroke volume with a very low EF if the ventricle is dilated and retaining too much blood after systole.

Can stroke volume be normal when cardiac output is low?

Yes. Cardiac output depends on both stroke volume and heart rate. A patient with a normal stroke volume can still have a low cardiac output if the heart rate is too slow, and the reverse is also true.

What does a high end-systolic volume suggest?

A higher-than-expected ESV often suggests impaired emptying from reduced contractility, high afterload, or both. It is one of the reasons the ejection fraction can fall even when EDV is large.

Reference: Otto CM. Textbook of Clinical Echocardiography. 6th ed. Elsevier, 2018.

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