QRS Axis Calculator

Calculate the QRS electrical axis from ECG lead voltages with this free online medical tool.

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About This Tool

The QRS Axis Calculator is a specialized tool for medical professionals, students, and healthcare enthusiasts to determine the electrical axis of the heart from standard ECG leads. By inputting the net QRS complex voltages from leads I, II, and III (or aVF), the tool calculates the mean electrical axis using the hexaxial reference system. This helps in diagnosing normal axis, left axis deviation, right axis deviation, or extreme axis deviation. The calculator provides instant, accurate results with a clear visual explanation of the findings.

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How to Use

Enter the net QRS voltage (in mm or mV) for leads I, II, and III (or aVF) in the input fields. Positive values indicate upward deflection, negative values indicate downward deflection.
Click the 'Calculate QRS Axis' button to process the inputs.
View the calculated axis in degrees and the clinical interpretation (normal, left deviation, right deviation, or extreme deviation) in the results section.
Use the 'Reset' button to clear all inputs and start over.

Frequently Asked Questions

Find Quick Answers

What is QRS axis and why is it important?

The QRS axis represents the overall direction of electrical depolarization in the ventricles during a heartbeat. It's important for diagnosing cardiac conditions like left ventricular hypertrophy, right ventricular hypertrophy, fascicular blocks, and other conduction abnormalities.

How do I determine net QRS voltage from an ECG?

Measure the amplitude of the QRS complex in each lead. Subtract the negative deflection (downward) from the positive deflection (upward) to get the net voltage. For example, if the R wave is +8 mm and the S wave is -2 mm, the net voltage is +6 mm.

What are the normal ranges for QRS axis?

Normal QRS axis ranges from -30° to +90°. Left axis deviation is between -30° and -90°, right axis deviation is between +90° and +180°, and extreme axis deviation (northwest axis) is between -90° and -180° (or +180° to +270°).

Can I use this tool for educational purposes?

Yes, this tool is designed for both clinical use and educational purposes. Medical students and healthcare professionals can use it to practice ECG interpretation and understand axis calculation principles.

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