# Cardiac Output Calculator

Calculate cardiac output (CO) from heart rate and stroke volume. Also calculates cardiac index (CI) when body surface area is provided. Normal ranges included.

## What this calculates

Cardiac output is the total volume of blood your heart pumps per minute. It depends on two things: how fast the heart beats and how much blood it pushes out with each beat. Enter the heart rate and stroke volume to calculate CO, and optionally provide body surface area for the cardiac index.

## Inputs

- **Heart Rate** (bpm) — min 20, max 250
- **Stroke Volume** (mL) — min 10, max 250 — Volume of blood pumped per heartbeat (typical: 60-100 mL)
- **Body Surface Area (optional)** (m²) — min 0.5, max 3 — Enter BSA to calculate cardiac index. Leave blank to skip.

## Outputs

- **Cardiac Output (CO)** — Total blood volume pumped per minute
- **Cardiac Index (CI)** — formatted as text — Cardiac output normalized to body surface area
- **CO Interpretation** — formatted as text — Whether the cardiac output is in the normal range
- **CI Interpretation** — formatted as text — Whether the cardiac index is in the normal range

## Details

Here's the formula:

**Cardiac Output (L/min) = Heart Rate (bpm) x Stroke Volume (mL) / 1000**

For a typical adult at rest with a heart rate of 72 bpm and a stroke volume of 70 mL, the cardiac output is about 5.0 L/min.

**Normal ranges:**

- **Cardiac output (CO):** 4.0-8.0 L/min at rest
- **Cardiac index (CI):** 2.2-4.0 L/min/m² (CO normalized for body size)
- **Stroke volume:** 60-100 mL per beat at rest

The cardiac index (CI = CO / BSA) is more clinically useful than raw CO because it adjusts for body size. A cardiac output of 4.5 L/min might be normal for a small person but inadequate for a large one.

**When cardiac output drops:**

- Below 4.0 L/min, tissues may not receive enough oxygen
- A cardiac index below 2.2 L/min/m² is one criterion for cardiogenic shock
- Heart failure, valve disease, and myocardial infarction can all reduce CO

**When cardiac output is elevated:**

- Sepsis, severe anemia, hyperthyroidism, and pregnancy all increase CO
- A cardiac index above 4.0 L/min/m² is considered a high-output state
- Exercise can temporarily increase CO to 20-25 L/min in trained athletes

In clinical practice, cardiac output is measured using thermodilution (Swan-Ganz catheter), echocardiography (Doppler), or arterial pulse contour analysis.

## Frequently Asked Questions

**Q: What is a normal cardiac output?**

A: Normal resting cardiac output for adults is 4.0-8.0 L/min. The average is about 5.0 L/min. The cardiac index (cardiac output divided by body surface area) is a better measure because it adjusts for body size. A normal cardiac index is 2.2-4.0 L/min/m².

**Q: How is stroke volume measured?**

A: In clinical settings, stroke volume is most commonly measured by echocardiography (ultrasound of the heart). The Doppler method measures blood flow velocity across the aortic valve and multiplies by the cross-sectional area of the outflow tract. Invasive methods include thermodilution via a pulmonary artery catheter. Normal resting stroke volume is 60-100 mL per beat.

**Q: Does cardiac output change with exercise?**

A: Yes, significantly. During intense exercise, cardiac output can increase 4-5 times above resting values. An untrained adult might reach 15-20 L/min, while elite endurance athletes can achieve 25-35 L/min. Both heart rate and stroke volume increase during exercise, though stroke volume plateaus at about 50-60% of maximum effort while heart rate continues to climb.

**Q: Why is cardiac index preferred over cardiac output?**

A: A 5-foot, 100-pound person and a 6-foot-4, 250-pound person have very different metabolic demands. A cardiac output of 4.5 L/min might be perfectly adequate for the smaller person but could signal low output in the larger one. The cardiac index divides CO by body surface area (BSA), putting everyone on the same scale. This is why ICU teams track CI rather than raw CO.

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Source: https://vastcalc.com/calculators/health/cardiac-output
Category: Health & Fitness
Last updated: 2026-04-08