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Stroke Volume Estimate Calculator

Enter your cardiac output and heart rate to estimate stroke volume.

Result

69.4 mL
5.00 L/min
Normal (55–100 mL)

How it is calculated

Cardiac output is the blood pumped per minute, so dividing it by the number of beats per minute gives the blood per beat: SV (mL) = CO (L/min) × 1000 ÷ HR (bpm). The factor 1000 converts litres to millilitres. Cardiac output must be entered in litres per minute and heart rate in beats per minute, and both must be above zero, otherwise no result is shown. The stroke volume is shown to one decimal. The tool also sorts it into a band: below 55 mL is labelled Low, 55 to 100 mL Normal, and above 100 mL High. These cut-offs are fixed in the tool and do not depend on age, body size or fitness. This is an arithmetic back-calculation, not a measurement, and it cannot replace echocardiography or a clinician's judgement.

Worked example

Cardiac output 5 L/min and a heart rate of 72 bpm. Convert to millilitres: 5 × 1000 = 5,000 mL per minute. Divide by the beats: 5,000 ÷ 72 = 69.4 mL per beat. That falls in the 55 to 100 mL band, so the label reads "Normal (55–100 mL)". Raising the heart rate to 100 bpm at the same 5 L/min would give 50.0 mL, which the tool labels Low.

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Common mistakes

  • Entering cardiac output in mL/min. The field expects litres per minute; typing 5000 gives a stroke volume a thousand times too large (69,444.4 mL).
  • Treating the Low, Normal or High label as a diagnosis. The cut-offs at 55 and 100 mL are the same for everyone, whatever the person's size or fitness.
  • Mixing readings taken at different times, such as cardiac output during exercise with a resting pulse. Both numbers must come from the same moment.
  • Confusing stroke volume with ejection fraction. Stroke volume is millilitres per beat; ejection fraction is a percentage of the ventricle's filling.
  • Using the result to make medical decisions. It is a derived figure whose accuracy depends entirely on the two inputs.

Sources

About this calculator

Stroke volume is the amount of blood the heart's left ventricle pumps out with each single beat, measured in milliliters. It relates directly to cardiac output (the total blood volume pumped per minute) and heart rate through the simple identity Stroke Volume = Cardiac Output / Heart Rate — rearranged and scaled to milliliters here to back-calculate SV from CO and HR.

Cardiologists and critical-care clinicians track stroke volume alongside ejection fraction to assess how efficiently the heart is pumping, since a low stroke volume despite a normal heart rate can signal reduced cardiac function — it's a routine figure in echocardiography reports and hemodynamic monitoring in intensive care.

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Comments (1)

  • Editorial team

    Body size matters: clinicians commonly divide stroke volume by body surface area to get an indexed value, because a smaller person can have a lower stroke volume that is normal for them. This tool uses one fixed band for everyone, so treat Low and High as prompts for the right context, not conclusions. Where do your cardiac output figures come from, a monitor, an echo report or course material?

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