How this calculator works
Sunglasses fit on three numbers: the lens width, the bridge and the temple length. The frame width is roughly the lens widths plus the bridge, and it should match the widest part of the face, usually the cheekbones, so the frame does not press on the temples or slide down. The calculator adds 2 mm to the cheekbone width as a starting point and divides the rest by two for the lens width. Face shape comes from comparing the forehead, cheekbones and jaw and from the ratio of face length to width. The shape advice is about balance: angular frames soften round features and curved frames soften square ones.
Formula
frame width = cheekbone width + 2 mm. lens width = (frame width - bridge, taken as 18 mm) / 2. face ratio = face length / cheekbone width. Shape: oblong if the ratio is 1.5 or more; diamond if the cheekbones are at least as wide as the forehead and wider than the jaw; heart if the forehead is more than 10 percent wider than the jaw; triangle if the jaw is more than 10 percent wider than the forehead; square or round from the feature description; otherwise oval.
Worked example
A face 14 cm across the cheekbones and 20 cm long has a ratio of 1.43. The cheeks are wider than both the 14 cm forehead and the 12 cm jaw, so the shape is diamond. The frame width to look for is 142 mm, and with an 18 mm bridge the lens width is about 62 mm.
Advertisement
Frequently asked questions
Where do I measure the cheekbone width?
Measure across the face at the most prominent part of the cheekbones, usually just below the outer corner of the eye, from one side to the other. Keep the tape straight and level; do not follow the curve of the face.
Is face shape really a reliable guide?
It is a rough styling heuristic, not a measurement standard. Many people have a mix of shapes, and the fit measurements matter more than the label. Use the shape advice to choose frames to try, then judge comfort and coverage in a mirror.
How do I read the numbers inside a frame?
A marking such as 52-18-140 means a 52 mm lens, an 18 mm bridge and a 140 mm temple. The frame width is roughly 52 + 52 + 18 = 122 mm. Compare that with the width this page suggests; if it is close, the frame is likely to fit.
Should the frame cover my eyebrows?
Usually the top of the frame should follow the brow line rather than cover it completely. A frame that sits too low can interfere with vision, and one that sits too high can look oversized. This is a style choice, not a rule.