Sunglasses Size Calculator

What the numbers on sunglasses mean

Look inside one of the arms, or on the bridge. You'll usually see three numbers, like 52□18-140 or 52-18-140:

The little square between the first two numbers comes from the "boxing system" for measuring frames, set out in the ISO 8624 standard. Our explainer on what the numbers on sunglasses mean goes into more detail.

How to measure your face width

You need a ruler or tape measure and a mirror.

1. Stand facing the mirror, looking straight ahead.
2. Hold the ruler horizontally just below your eyes.
3. Measure from your left temple to your right temple, the flat area beside each eye where the arms of sunglasses sit.
4. Write the number down in millimetres.

That's your face width. Most adults measure somewhere between about 120 and 155 mm. Our guide on how to measure your face for sunglasses has photos.

Sunglasses size chart

The calculator matches face width to frame width using this chart, the same one in our sunglasses size chart:

Estimating total frame width from the numbers

Retailers don't always list total frame width, but you can estimate it: two lens widths, plus the bridge, plus about 10 mm for the frame edges and hinges.

It's an estimate, because thick acetate frames add more than thin metal ones. That's why the calculator calls it "approximate." If a retailer lists the real total width, use that.

Lens width, bridge and temple: which matters most

• Lens width and bridge together decide how wide the frame is, and whether your eyes sit near the centre of each lens. These matter most.
• Bridge width also decides comfort on your nose. Too narrow and the frame pinches or sits high; too wide and it slides down.
• Temple length matters least. Most adults wear 135 to 150 mm, and an optician can adjust the bend behind the ear.

If you're copying a pair that fits, stay within about 2 mm on lens and bridge and about 5 mm on temple length.

Bridge fit and low-bridge frames

If sunglasses always slide down your nose or rest on your cheeks when you smile, the problem is usually the bridge, not the size. Many brands now make low-bridge or "alternative fit" frames with taller nose pads that lift the frame away from the cheeks. Frames with adjustable nose pads on metal arms are also more forgiving than moulded plastic bridges.

Frame size and face shape

Size first, style second. Once the width is right, these pairings are a good starting point:

Our guide to the best glasses by face shape has examples.

Oversized, sport and kids' sunglasses

• Oversized sunglasses are deliberately wider than the face. Expect frame widths of 145 mm or more, and check that they don't press on your temples.
• Sport sunglasses wrap around the face, so the numbers can be hard to compare. Look for the maker's fit guide (small, medium, large face).
• Children's sunglasses usually have lens widths of about 40 to 48 mm and shorter arms. Measure the child's face the same way.

How sunglasses should fit

• The frame is about as wide as your face, without pressing on your temples.
• Your eyes sit near the centre of each lens.
• The bridge sits flat on your nose without pinching.
• The frame doesn't touch your cheeks when you smile.
• The arms rest on your ears without digging in behind them.
• The glasses stay put when you look down.

For prescription eyewear, there's more to check, like pupillary distance and lens height; see our eyeglasses size chart.

Worked examples

• A 133 mm face. The calculator recommends frames about 128 to 137 mm wide, which is the classic 52-18-140 size.
• A pair labelled 55-19-145. Two lenses of 55, plus 19, plus about 10 mm: roughly 139 mm, which suits a face of about 135 to 140 mm.
• A 148 mm face. That's large: look for frames around 143 to 152 mm, such as 57-20-150.
• Copying a pair that fits. If your favourite pair is 54-17-145, look for 52 to 56 lenses and 15 to 19 bridges; anything in that window will fit similarly.

Lens height and coverage

Width isn't the only dimension. Lens height, from the top to the bottom of the lens, decides how much of your field of view is shaded and whether light gets in underneath. Deeper lenses give more coverage, which helps for driving, water and snow. Shallow, narrow lenses look sleek but let in more light around the edges. If you wear sunglasses for sport, wraparound frames block light from the sides.

UV protection and lens categories

Size affects comfort and coverage; the lens decides how well your eyes are protected.

• UV protection: look for lenses labelled UV400 or "100% UV protection," which block UVA and UVB.
• Standards: sunglasses sold in the EU are tested to EN ISO 12312-1, and in the US to the ANSI Z80.3 standard.
• Filter categories: under ISO 12312-1, lenses are graded from category 0 (very light) to category 4 (very dark). Category 2 and 3 are typical sunglasses; category 4 is too dark for driving.
• Polarised lenses cut glare from water, roads and snow. They don't change UV protection on their own, so still check the UV rating.

Sunglasses for children

Children's eyes let more UV through to the retina than adults', so good UV protection matters for kids. Look for UV400 lenses, flexible frames that survive being sat on, and a strap for young children. Measure their face width the same way and choose small frames, usually with lenses of about 40 to 48 mm.

How to read a sunglasses listing online

When you shop online, look for these details before you buy:

1. The three numbers (lens, bridge, temple). If they're missing, ask, or look for them in the product photos of the inside arm.
2. Total frame width. Some retailers list it; if not, estimate it with the calculator.
3. Lens height, especially if you want good coverage.
4. Fit notes, such as "low bridge fit," "narrow fit" or "oversized."
5. Lens details: UV400, polarised or not, and the filter category.
6. Return policy, in case the fit isn't right.

Compare the numbers with a pair you already own. If your favourite pair is 52-18-140, anything within about 2 mm on the first two numbers will fit similarly.

Prescription sunglasses

Prescription sunglasses need the same frame size as your regular glasses, plus your pupillary distance (PD) so the optical centres line up with your eyes. Very wide or wrapped frames can be harder to glaze for strong prescriptions, so check with the retailer. Our eyeglasses size chart explains PD, lens height and frame fit for prescription eyewear.

If you sell sunglasses online

Fit is the main reason sunglasses come back, because shoppers can't try them on. On your product pages:

• Show lens width, bridge, temple and total frame width for every frame.
• Group frames into small, medium and large with millimetre ranges.
• Explain how to find the numbers on a pair the shopper already owns.
• Note whether a frame has a low-bridge option.

Our size guide for sunglasses brands covers the setup.

Frequently asked questions

Sources and standards

1. EN ISO 12312-1, Sunglasses and related eyewear for general useDefines sunglass filter categories 0 to 4; category 4 is not suitable for driving.
2. ANSI Z80.3, Nonprescription sunglass and fashion eyewear requirementsThe US standard for sunglasses.
3. ISO 8624, Ophthalmic optics: Spectacle frames, measuring system and terminologyDefines the boxing system behind the lens and bridge numbers on frames.
4. Tailor Size Guide sunglasses size chartThe face-width to frame-width table the calculator uses.