Normal axis lying between 0 degrees and 90 degrees
If lead 1 QRS deflection is about the same as aVF lead deflection then QRS axis is between 40 and 50 degrees
If lead 1 QRS deflectin exceeds aVF then QRS axis is between 0 and 40 degrees
If aVF lead deflection is greater than QRS axis is between 50 and 90 degrees
LAD or Left Axis deviation - mean QRS axis < -30 degrees
Source