What this calculator does
Stroke volume is the amount of blood the left ventricle ejects with each heartbeat. It is found from two ultrasound or MRI measurements: end-diastolic volume, the amount of blood in the ventricle just before it contracts, and end-systolic volume, what is left just after. The difference between the two is the stroke volume for that beat.
On its own, stroke volume is one figure in a larger picture of heart function. Doctors more often quote ejection fraction, which expresses stroke volume as a percentage of end-diastolic volume, because that percentage stays comparable across people with different heart sizes. This calculator works out both from the same two inputs.
The formula
Subtract end-systolic volume from end-diastolic volume to get stroke volume. Dividing that stroke volume by end-diastolic volume, then multiplying by 100, gives the ejection fraction. If a heart rate is entered as well, multiplying stroke volume by heart rate gives cardiac output, the volume pumped per minute.
| Term | Meaning |
|---|---|
| EDV | End-diastolic volume: the volume of blood in the left ventricle just before it contracts, at its fullest point. |
| ESV | End-systolic volume: the volume of blood remaining in the left ventricle just after it contracts, at its emptiest point. |
| Stroke volume | The volume ejected in one beat: EDV − ESV. |
| Ejection fraction | Stroke volume as a percentage of EDV, the more commonly quoted clinical figure. |
The inputs explained
| Field | What to enter |
|---|---|
| End-diastolic volume (EDV) (mL) | End-diastolic volume, usually reported from an echocardiogram or cardiac MRI. |
| End-systolic volume (ESV) (mL) | End-systolic volume, from the same scan. |
| Heart rate (optional, for cardiac output) (bpm) | Optional. Enter a resting or measured heart rate to also see cardiac output. |
When to use it
Reading an echocardiogram report
Echo and MRI reports usually list EDV and ESV directly. Working out the stroke volume and ejection fraction from those two figures checks the maths behind a summary percentage, or fills in the stroke volume when only the percentage was given.
Tracking fitness-related changes over time
Endurance training tends to increase resting stroke volume as the heart adapts, which is one reason trained athletes often have a lower resting heart rate for the same cardiac output.
Following up after a diagnosis
Stroke volume and ejection fraction are tracked over repeat scans to see whether heart function is stable, improving or declining, alongside whatever a cardiologist is watching for clinically.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How stroke volume and ejection fraction change with end-systolic volume
A fixed 120 mL end-diastolic volume, against a range of end-systolic volumes.
| End-systolic volume | Stroke volume | Ejection fraction | Cardiac output at this heart rate |
|---|---|---|---|
| 30 mL | 90 mL | 75.0% | 6.30 L/min |
| 40 mL | 80 mL | 66.7% | 5.60 L/min |
| 50 mL | 70 mL | 58.3% | 4.90 L/min |
| 60 mL | 60 mL | 50.0% | 4.20 L/min |
| 70 mL | 50 mL | 41.7% | 3.50 L/min |
| 80 mL | 40 mL | 33.3% | 2.80 L/min |
How stroke volume and ejection fraction change with end-diastolic volume
A fixed 50 mL end-systolic volume, against a range of end-diastolic volumes.
| End-diastolic volume | Stroke volume | Ejection fraction | Cardiac output at this heart rate |
|---|---|---|---|
| 80 mL | 30 mL | 37.5% | 2.10 L/min |
| 100 mL | 50 mL | 50.0% | 3.50 L/min |
| 120 mL | 70 mL | 58.3% | 4.90 L/min |
| 140 mL | 90 mL | 64.3% | 6.30 L/min |
| 160 mL | 110 mL | 68.8% | 7.70 L/min |
| 180 mL | 130 mL | 72.2% | 9.10 L/min |
Questions
What is a normal stroke volume?
Resting stroke volume in a healthy adult is roughly 60 to 100 mL, though it varies with body size, sex, fitness and the specific measurement method used. There is no single number that applies to everyone, which is why it is usually interpreted alongside ejection fraction rather than on its own.
What is the stroke volume formula?
Stroke volume equals end-diastolic volume minus end-systolic volume: the amount of blood in the ventricle before it contracts, minus what is left after. Both figures come from the same imaging study, such as an echocardiogram.
Why do doctors usually talk about ejection fraction instead of stroke volume?
Ejection fraction expresses stroke volume as a percentage of end-diastolic volume, which makes it comparable between people with differently sized hearts. Two people can have the same 70 mL stroke volume with very different ejection fractions if their ventricles are different sizes.
Can this calculator diagnose a heart problem?
No. It only works out the arithmetic behind two measurements you already have. Interpreting what a given stroke volume or ejection fraction means for a specific person is a clinical judgement for a doctor, who has the full scan and history to go with it.
To see the same figures expressed as a percentage, use the ejection fraction calculator. For the volume pumped per minute rather than per beat, see the cardiac output calculator.