Sunglasses Sizes: How to Read the Numbers and Find Your Fit
For anyone buying sunglasses online who wants them to fit like a pair they already own. The three numbers printed inside the arm tell you almost everything; this explains them and how to turn them into a frame width.
Sunglasses are sized by three numbers in millimeters, printed inside one arm: lens width, bridge width and temple (arm) length, for example 52-18-145. Adult lenses run about 45–62 mm, bridges 14–24 mm and temples 130–150 mm. The overall frame front is roughly two lenses plus the bridge plus 6–12 mm, so a 52-18 frame is about 128–134 mm (5.0–5.3 in) wide.
- Lens width
- 45–62 mm (adult)
- Bridge
- 14–24 mm
- Temple length
- 130–150 mm
- Medium frame
- ≈ 130–140 mm wide
On this page
What the three numbers mean
Look on the inside of the left or right temple (arm) or on the bridge. You will find the model number, a color code and a set of three numbers, sometimes with a small square between the first two: 52□18 145.
The square symbol means the lens is measured as the box that encloses it (the boxing system in ISO 8624), so a round 50 mm lens and a square 50 mm lens are both 50 mm at their widest. Some makers add a fourth number for lens height, often on the box or product page rather than the frame. Lens height matters for tall frames and for prescription sunglasses with progressive lenses.
Sunglasses size chart
The categories below are how most retailers group adult frames. Total width is the measurement that decides whether a frame suits your face; it is not printed on the frame, so the chart estimates it from the lens and bridge.
| Size | Lens width | Bridge | Temple | Approx. total width |
|---|---|---|---|---|
| Small / narrow | 46–50 mm | 14–18 mm | 130–140 mm | Under 130 mm (5.1 in) |
| Medium | 51–55 mm | 16–20 mm | 140–145 mm | 130–140 mm (5.1–5.5 in) |
| Large / wide | 56–62 mm | 16–22 mm | 140–150 mm | Over 140 mm (5.5 in) |
| Children | 40–48 mm | 14–17 mm | 115–130 mm | About 105–120 mm |
Total frame width is approximately 2 × lens width + bridge + 6 to 12 mm, the extra being the frame rims and hinges (end pieces). Thick acetate frames sit at the upper end of that allowance; thin metal frames at the lower end. If the product page lists "frame width" or "total width", use that figure instead.
How to find your size
- Start with a pair that fits. Read the three numbers inside the arm of any glasses or sunglasses that sit well. Frames within about 2 mm on lens width and bridge, and 5 mm on temple length, will fit similarly.
- Measure the frame front. If the numbers have worn off, lay the glasses face down and measure straight across the front from hinge to hinge. That is the total width to match.
- No glasses to copy? Measure your face. Stand in front of a mirror and hold a ruler horizontally just below your eyes. Measure from temple to temple, at the point where the arms of glasses would pass. Choose a total frame width within a few millimeters of that number.
- Check the bridge. If glasses usually slide down your nose or leave marks, the bridge is too wide or too narrow. Low or flat nose bridges suit frames with adjustable nose pads or a "low bridge fit" version.
- Check the temple length. The arm should reach past the top of the ear and bend down behind it. Most adults wear 140 to 145 mm; 135 mm suits smaller heads, 150 mm larger ones.
With the sunglasses on, your eyes should sit near the center of each lens, the frame should not press on your temples, and the lenses should not rest on your cheeks when you smile.
Sizes of well-known models
Many classic frames come in two or three sizes, and the difference between them is bigger than it looks on a product photo. The bridge often changes along with the lens.
| Model | Lens | Bridge | Temple |
|---|---|---|---|
| Wayfarer RB2140, size 50 | 50 mm | 22 mm | 150 mm |
| Wayfarer RB2140, size 54 | 54 mm | 18 mm | 150 mm |
| Aviator RB3025, size 55 | 55 mm | 14 mm | 135 mm |
| Aviator RB3025, size 58 | 58 mm | 14 mm | 135 mm |
| Aviator RB3025, size 62 | 62 mm | 14 mm | 135–140 mm |
The Wayfarer is a useful example of why one number is not enough. The size 54 has wider lenses but a narrower bridge than the size 50, so the two fronts are close in total width (about 122 mm vs 126 mm before end pieces) while sitting on the nose very differently. Retailers sometimes list slightly different temple lengths for the same model, so check the listing.
Lens categories: how dark sunglasses are
Size is half of the label. In Europe, the UK and many other countries, sunglasses are marked with a filter category from 0 to 4 under ISO 12312-1, which sets how much visible light the lenses let through. In the US, ANSI Z80.3 covers nonprescription sunglasses.
| Category | Visible light transmitted | Use |
|---|---|---|
| 0 | 80–100% | Clear or very light tint; fashion, overcast days |
| 1 | 43–80% | Light tint; low sunlight |
| 2 | 18–43% | Medium tint; general use |
| 3 | 8–18% | Dark tint; bright sun, beach, most everyday sunglasses |
| 4 | 3–8% | Very dark; glaciers and high mountains. Not suitable for driving. |
Darkness and UV protection are separate. A lightly tinted lens can block all UV, and a dark lens without UV filtering can be worse than none because the pupils open wider behind it. Look for UV400 or "100% UV protection" on the label.
Common sizing mistakes
- Judging by product photos. Most are shot at the same scale regardless of size; compare millimeters, not pictures.
- Matching lens width only. A 2 mm wider lens with a 4 mm narrower bridge gives a frame of the same total width but a different fit on the nose.
- Ignoring wrap. Sport and wraparound frames curve around the face, so their flat-measured width overstates how wide they look on you. Use the maker's fit guide.
- Forgetting the hat. Long temples can clash with a cap or helmet strap. The hat size chart helps if you wear both, and the watch size guide uses the same millimeter-based sizing.
Frequently asked questions
What does 54□18 145 mean on sunglasses?
54 mm lens width, 18 mm bridge (the gap between the lenses) and 145 mm temple length. The square symbol means the lens was measured with the boxing system, the method defined in ISO 8624.
How do I know if sunglasses are too big?
Your eyes should sit roughly in the horizontal center of each lens, the frame should not extend more than a few millimeters past the sides of your face, and the glasses should not slide down when you look at the floor. If your eyes sit close to the inner edge of the lenses, the frame is too wide.
What size sunglasses for a small face?
Look for lens widths of about 46 to 51 mm, a total frame width under about 130 mm and temples of 135 to 140 mm. Many brands also sell a small or narrow fit of popular models.
Are men's and women's sunglasses sizes different?
The numbers mean the same thing for everyone. Frames marketed to men tend to be larger, typically 54 to 62 mm lenses and 140 to 150 mm temples, while women's styles cluster around 50 to 56 mm, but face width matters more than the label.
What size are kids' sunglasses?
Children's frames commonly have lens widths of about 40 to 48 mm, bridges of 14 to 17 mm and temples of 115 to 130 mm. Toddler frames are smaller still and often use a strap instead of temples.