Mean QRS Axis (frontal plane, hexaxial)
Mean frontal-plane QRS axis from net lead I and aVF deflections, with the quadrant interpretation.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Net QRS deflection in lead I
- 8 mm, signed
- Net QRS deflection in lead aVF
- 6 mm, signed
Result: Mean QRS axis 36.9 deg, normal axis (-30 deg to +90 deg).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Quadrants
- Normal -30 to +90 deg; left-axis deviation -30 to -90 deg; right-axis deviation +90 to +180 deg; extreme/northwest -90 to -180 deg.
- Indeterminate
- Both lead I and aVF isoelectric (0) gives no axis; the result is surfaced as indeterminate, never 0 deg.
What you enter
- Net QRS deflection in lead I
- Net QRS deflection in lead aVF
- Net QRS deflection in lead II (optional)
How this is calculated
- Formula
- Mean frontal-plane axis = atan2(net aVF, net lead I); lead I = 0 deg, aVF = +90 deg (an orthogonal pair).
Surawicz B, Knilans T. Chou's Electrocardiography in Clinical Practice: Adult and Pediatric. 6th ed. Saunders/Elsevier; 2008 (standard hexaxial reference for the frontal-plane QRS axis). Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.
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