What is the cardiac output?
Work out cardiac output from heart rate and stroke volume, or by the Fick principle, and the cardiac index over the body surface area. For information only. This is not medical advice or a diagnosis. Do not use it to make treatment decisions without a clinician. No licensed clinician has reviewed this page.
- Cardiac output (L/min)
- 4.9
The cardiac output is 4.9 L/min, a cardiac index of 2.51 L/min/m².
- Cardiac index (L/min/m²)
- 2.51
- Body surface area (m²)
- 1.95
Cardiac output (L/min): 4.9. The cardiac output is 4.9 L/min, a cardiac index of 2.51 L/min/m².
Cardiac output in L/min
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
Works out cardiac output from heart rate and stroke volume, or by the Fick principle from oxygen use and blood oxygen levels, with the cardiac index over the body surface area.
Example with the default inputs (Method HR × SV, Heart rate (beats/min) 70, Stroke volume (mL) 70, Height 5 ft 10 in, Weight 170 lb): The cardiac output is 4.9 L/min, a cardiac index of 2.51 L/min/m².
Method: CO = HR × SV ÷ 1,000 (L/min). Fick: CO = VO2 ÷ ((CaO2 − CvO2) × 10), with O2 content = 1.34 × Hb × saturation + 0.003 × PO2 (mL/dL). CI = CO ÷ BSA, BSA = √(cm × kg ÷ 3,600) (Mosteller).
- The Fick method needs a mixed venous sample from the pulmonary artery and a measured or estimated oxygen use.
- Hemoglobin carries 1.34 mL of oxygen per gram when fully saturated; plasma carries 0.003 mL/dL per mmHg.
- The page shows the arithmetic for measured values. It is not a measurement and not a diagnosis.
Worked examples
Each example is checked against the calculator on every build.
- Method HR × SV, Heart rate (beats/min) 70, Stroke volume (mL) 70, Height 5 ft 10 in, Weight 170 lb gives Cardiac output (L/min) 4.9, Body surface area (m²) 1.951515, Cardiac index (L/min/m²) 2.510869.Source: Demir 2025 and Mosteller 1987: CO = HR × SV = 70 × 70 = 4,900 mL/min = 4.9 L/min
- Method HR × SV, Heart rate (beats/min) 60, Stroke volume (mL) 80, Height 5 ft 10.9 in, Weight 176.4 lb gives Cardiac output (L/min) 4.8, Body surface area (m²) 2, Cardiac index (L/min/m²) 2.4.
- Method Fick, Oxygen use, VO2 (mL/min) 250, Hemoglobin (g/dL) 15, Arterial saturation, SaO2 98%, Mixed venous saturation, SvO2 75%, Arterial PO2 (mmHg) 95, Mixed venous PO2 (mmHg) 40, Height 5 ft 10.9 in, Weight 176.4 lb gives Cardiac output (L/min) 5.221387, Arterial-venous O2 difference (mL/dL) 4.788, Body surface area (m²) 2, Cardiac index (L/min/m²) 2.610693.Source: Fick with the Nebout 2012 oxygen content: CaO2 = 1.34 × 15 × 0.98 + 0.003 × 95 = 19.983
Medical disclaimer
This calculator is for information and education only. It is not medical advice, and its result is not a diagnosis. Do not use it to start, stop, or change a treatment without a clinician who knows your health history. No licensed clinician has reviewed this page. This site's editors checked the formulas and worked examples against published sources. If you think you have a medical emergency, call your local emergency number.
When this does not apply. The Fick method needs a true mixed venous sample (from the pulmonary artery) and a steady state; it is less reliable with shunts in the heart or a changing oxygen use. The cardiac index uses the Mosteller body surface area for adults and children; it is an estimate.
How it is worked out
Heart rate × stroke volume. CO (L/min) = HR (beats/min) × SV (mL) ÷ 1,000.
Fick.
- CaO2 (mL/dL) = 1.34 × Hb (g/dL) × SaO2 ÷ 100 + 0.003 × PaO2 (mmHg).
- CvO2 (mL/dL) = 1.34 × Hb × SvO2 ÷ 100 + 0.003 × PvO2.
- CO (L/min) = VO2 (mL/min) ÷ ((CaO2 − CvO2) × 10). The 10 turns mL/dL into mL/L.
- If CaO2 − CvO2 is under 0.1 mL/dL, the page gives no answer and asks you to check the values.
Cardiac index. BSA (m²) = √(height cm × weight kg ÷ 3,600) (Mosteller 1987); CI = CO ÷ BSA.
Height typed in feet and inches is × 2.54 cm per inch; weight in lb is × 0.45359237 kg. The arithmetic runs on the exact typed decimals; only the square root is a float. Every result is shown to 2 decimals.
Worked examples by hand
Page default. 70 × 70 ÷ 1,000 = 4.90 L/min. 5 ft 10 in = 177.8 cm; 170 lb = 77.1107029 kg. BSA = √(177.8 × 77.1107029 ÷ 3,600) = √3.80838 = 1.95 m². CI = 4.9 ÷ 1.9515 = 2.51 L/min/m².
HR 60, SV 80, 180 cm, 80 kg. CO = 4.80 L/min. BSA = √(180 × 80 ÷ 3,600) = √4 = 2.00 m². CI = 2.40.
Fick. VO2 250, Hb 15, SaO2 98%, SvO2 75%, PaO2 95, PvO2 40, 180 cm, 80 kg. CaO2 = 1.34 × 15 × 0.98 + 0.003 × 95 = 19.698 + 0.285 = 19.983. CvO2 = 1.34 × 15 × 0.75 + 0.003 × 40 = 15.075 + 0.12 = 15.195. Difference 4.79 mL/dL (4.788). CO = 250 ÷ 47.88 = 5.22 L/min. CI = 5.2214 ÷ 2 = 2.61.
Other questions people ask
How is cardiac output calculated?
Cardiac output is the blood the heart pumps each minute: heart rate × stroke volume. At 70 beats a minute and 70 mL a beat, it is 4,900 mL, or 4.9 L a minute.
What is the Fick method?
The Fick principle says the oxygen the body uses each minute equals the blood flow times the oxygen the blood gives up. So cardiac output = oxygen use (VO2) ÷ (arterial oxygen content − mixed venous oxygen content).
How is oxygen content worked out?
Oxygen content (mL per dL of blood) = 1.34 × hemoglobin (g/dL) × saturation + 0.003 × PO2 (mmHg), as in Nebout 2012. Hemoglobin carries most of the oxygen; the second term is the small amount dissolved in plasma. Some sources use 1.39 and 0.0031 instead, which gives a slightly different result.
What is the cardiac index?
Cardiac output divided by body surface area, so people of different sizes can be compared. The page uses the Mosteller body surface area, √(height in cm × weight in kg ÷ 3,600).
Where does the VO2 come from?
Ideally it is measured from the breath. When it is estimated, the Fick result is only as good as the estimate, so the page asks for the value and does not assume one.
Does the page measure cardiac output?
No. It does the arithmetic on values measured elsewhere, such as an echo stroke volume or blood gas results.