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How-To

How to Size and Adjust Sunglasses

Frame width, base curve, and nose pads — the three adjustments that fix most fit complaints.

Written by William • Updated August 2026 • 5 min read

Most sunglasses complaints are fit complaints wearing a different disguise. Slipping, pinching, lens contact with eyelashes, and gaps that let light in are all sizing issues, and several are adjustable on frames you already own.

  1. 1

    Measure frame width against your face

    The frame should be roughly as wide as your face at the temples, with the lens edges sitting just inside or level with the outer edge of your face. Too narrow pinches; too wide slides. Manufacturer measurements are usually printed inside the temple arm as three numbers: lens width, bridge width, and temple length.

  2. 2

    Understand base curve

    Base curve describes how much a lens wraps. Base 6 is mild and suits everyday frames; base 8 is a steep sport wrap that hugs the face and blocks peripheral light. A steeper wrap gives better coverage and is harder to fit with a prescription and less comfortable for some face shapes.

    Prescription optionsWhy base curve limits Rx frames
    Read Guide →
  3. 3

    Adjust the nose pads first

    On frames with metal nose pad arms, gently squeezing them together raises the lens and tightens the grip; spreading them lowers and loosens. This one adjustment fixes slipping, lenses touching cheeks, and eyelashes brushing the lens — three of the most common complaints.

  4. 4

    Adjust temple arms with heat, carefully

    Acetate temple arms can be warmed gently and bent to hook better behind the ear. This is best done by an optician, since overheating warps the frame permanently. Never use boiling water or a heat gun at home on frames you care about.

  5. 5

    Diagnose by symptom

    Sliding down the nose means the bridge is too wide or the pads too open. Pressure behind the ears means the frame is too narrow. Light leaking in at the sides means the base curve is too flat for your face. Lenses touching eyelashes means the pads are set too low.

    Fit and face shapeChoosing the right frame shape to start with
    Read Guide →
  6. 6

    When the answer is a different design

    If nothing fits because your head is wide, narrow, or you wear a hat constantly, a cord-arm design sidesteps the whole problem by making fit adjustable rather than fixed. That is a genuine solution rather than a workaround for people at the edges of standard sizing.

    Armless designsWhy removing arms fixes fit problems
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Fit Problems and Fixes

SymptomCauseFix
Slides down the noseBridge too wide, pads openSqueeze nose pads together
Pressure behind the earsFrame too narrowWider frame or adjustable temples
Light leaks at the sidesBase curve too flatSteeper wrap, base 8
Eyelashes touch the lensPads set too lowRaise the pads
Lenses rest on cheeksFrame too tall or pads lowSmaller lens height
Nothing fitsHead outside standard sizingCord-arm or adjustable design

Frequently Asked Questions

What do the numbers inside the temple mean?
Lens width, bridge width, and temple arm length, all in millimetres. Comparing them against a pair that already fits you is the fastest way to buy online successfully.
Can I adjust plastic frames myself?
Cautiously and only with gentle warmth. Acetate can be reshaped and nylon sport frames generally cannot. An optician will usually adjust them free in a few minutes.
Does face shape really matter?
For appearance, somewhat. For function, frame width and base curve matter far more, and those are measurable rather than subjective.