You can figure out what size sunglasses you need by checking a few key measurements and matching them to simple size ranges (small, medium, large) plus your face width and shape.

Quick Scoop

  • Sunglasses size is mainly about lens width , bridge width, and temple (arm) length.
  • For most adults, “small / medium / large” sizes follow predictable millimeter ranges you can use even when shopping online.
  • A fast hack: measure your face width (temple to temple) and match it to a lens-width range in mm.

Step 1 – Understand the numbers on frames

Most sunglasses have three numbers printed inside the arm, like: 55–17–140.

  • First number = lens width (mm)
  • Second = bridge width (mm)
  • Third = temple length (mm)

These three tell you how wide the front is, how it sits on your nose, and how far the arms reach behind your ears.

Step 2 – Match to size (small / medium / large)

A common size guide looks like this:

[1][5] [1] [5][1] [5][1] [1] [5][1] [1][5] [1] [5][1]
Overall size Lens width (mm) Bridge width (mm) Temple length (mm)
Small face ≈ 49–54≈ 14–18≈ 130–135
Medium face ≈ 55–58≈ 16–20≈ 135–140
Large face ≈ 59–63≈ 18–22≈ 140–145+
Typical adult sunglasses lens widths overall run roughly 49–62 mm, bridges about 16–24 mm, and temples about 135–150 mm.

Step 3 – Measure your face in 1 minute

You can do this with a ruler or tape in front of a mirror.

  1. Face width (temple to temple)
    • Hold the ruler horizontally across your face at eyebrow level and measure from one temple to the other.
  1. Classify your face width
    • Narrow: less than ~129 mm → look for lenses up to ~50 mm.
 * Average: 130–139 mm → lenses around 51–55 mm usually work.

 * Wide: 140 mm+ → lenses 56 mm and above.

You don’t need perfection; most people are comfortable in a small range rather than one exact number.

Step 4 – Check how they should fit

Once you know your range, the right sunglasses should:

  • Not extend way past your temples and not look pinched or too narrow.
  • Sit lightly on your nose without sliding or pinching (bridge size too small = squeeze, too big = slipping).
  • Have arms long enough to reach just behind your ears without digging in or popping off (temple length).

If you already own a pair that fits well, use its numbers as your baseline and stay within ±2–3 mm on lens width and ±2 mm on bridge width.

Step 5 – Factor in your face shape

Size is about physical fit; shape is about how they look on you.

  • Oval face: Most styles work; medium lens widths that are as wide or slightly wider than your face look balanced.
  • Round face: Go a bit wider with more angular frames to add definition.
  • Square face: Slightly larger round or oval frames help soften strong angles.
  • Heart / diamond: Frames that balance a broader forehead or highlight high cheekbones (like cat-eye or rimless) work well.

You can treat these as style tips, not strict rules—comfort and confidence win.

Fast “What Size Do I Need?” shortcuts

If you want ultra-quick guidance:

  • Narrow / small head → try lens width around 49–52 mm, small–medium bridge, 130–135 mm temples.
  • Average head → start at 53–56 mm lenses, mid bridge (16–20 mm), 135–140 mm temples.
  • Bigger head → 57–60+ mm lenses and 140 mm+ temples so the frame doesn’t pinch.

If you tell me your face width in mm (or send the numbers from a pair you own), I can suggest an exact size range for your next sunglasses.

Information gathered from public forums or data available on the internet and portrayed here.