Step 1. Pull your hair back and use your ruler to measure from ear to ear stopping at where the ear begins (width) and from the top of your forehead to the bottom of your chin (length). Your ratio of width to length should be 1 to 1, 1 to 1 1/2, or 1 to 2.
Step 2. Use the tape measure to measure your forehead, cheeks, and jaw at the widest points.
Oval-your width to length ratio is 1 1/2
Long-your width to length ratio is more than 1 to 1 1/2
Round-forehead, cheekbones, and jaw are equal, round jaw, soft features, your width to length ratio is 1 to 1
Square-forehead, cheekbones, and jaw are equal, sharp jawline, angular features, your width to length ratio is 1 to 1 OR 1 to 1 1/2
Heart-wider at the forehead and more narrow at the jawline, possible pointy chin, looks like inverted triangle
Diamond-widest at your cheekbones, jawline and forehead are the same length
Choosing your sunglasses based on your face shape:
Oval-this face shape can pretty much wear any shape...lucky you!
Long-avoid small frames, look for square or rectangle shapes
Round-angular frames look best to add definition and accentuate your bone structure, square shapes
Square-circular, soft shapes to balance out the strong jawline
Heart-Aviator frames look the best to soften and balance your features, choose frames that broaden the jawline
Diamond-choose curved frames like oval or cat eye to widen the face and balance the jaw line