Click anywhere on the circle or drag the white knob. The diagram updates the axis degree, classification, and the classic Lead I / aVF / II logic in real time.
Lead I: 0°
aVF: +90°
Lead II: +60°
Normal: −30° to +90°
Current axis
+60°
Fast verdict
Normal
Quadrant logic
lights live
I
Positive if QRS points toward left arm, around 0° hemisphere.
+
aVF
Positive if QRS points inferiorly, toward +90° hemisphere.
+
II
Positive helps distinguish true LAD from borderline normal.
+
Axis class
Normal axis
−30° to +90°
I positive + aVF positive = easy normal. If aVF is negative, check Lead II.
+60°mean QRS
Try presets
or scrub
−180°+180°
Exam pearl: Normal axis is usually −30° to +90°. If Lead I is positive and aVF negative, Lead II decides: II positive = still normal/borderline; II negative = left-axis deviation.
Axis ranges to memorize
Normal−30° to +90°
Left-axis deviation−30° to −90°
Right-axis deviation+90° to +180°
Extreme / northwest−90° to −180°
Boundary convention varies slightly by source; this uses the common exam-friendly cutoffs. At exactly −30° or +90°, correlate with QRS morphology and clinical context.
Tap-check: what do the leads suggest?
Use the presets or drag first, then quiz yourself on the quadrant pattern.