Glasses are labelled with three numbers like 52-18-140: lens width, bridge width and temple (arm) length in millimetres. A good fit has the frame about as wide as your face at the temples, with your eyes near the centre of each lens. Face shape guides style: angular frames balance round faces, round frames soften square ones.
How to use the Sunglasses Size Calculator
- Face width at temples
- Bridge width
- Forehead width
- Cheekbone width
- Jawline width
- Face length
Results update as you type, and every field accepts the units shown in its menu.
How it works
Measure across your forehead, across the widest part of your cheekbones, along your jawline and from hairline to chin, and your face width at the temples.
Frames by face shape
| Face shape | Frames that suit |
|---|---|
| Oval | Almost any – try oversized or geometric |
| Round | Rectangular, square or angular frames |
| Square | Round, oval or aviator frames |
| Heart | Bottom-heavy, round or rimless frames |
| Diamond | Cat-eye, oval or rimless frames |
| Oblong | Tall, wide or oversized frames |
Tips
- Measure over thin clothing with a soft tape held snug but not tight, and keep the tape level all the way round.
- Take each measurement twice; if you are between sizes, the larger size is usually the safer choice.
- Size charts vary by brand and country – check the maker’s own chart when it is available.
- For sewing projects, pre-wash fabric before cutting and buy 10% extra for shrinkage, pattern matching and mistakes.
Common mistakes to avoid
- Mixing inches and centimetres between the tape and the size chart.
- Forgetting seam and hem allowances when cutting fabric.
- Measuring an old, stretched garment instead of your body.
Inputs explained
| Field | What to enter |
|---|---|
| Face width at temples | Units: mm, cm, in |
| Bridge width | Units: mm |
| Forehead width | Units: cm, in, mm, m |
| Cheekbone width | Units: cm, in, mm, m |
| Jawline width | Units: cm, in, mm, m |
| Face length | Units: cm, in, mm, m |
What each result means
- Ideal lens width = ([Face width at temples] – [Bridge width] – 0.01)÷2
- Typical temple (arm) length = clamp([Face width at temples]×1.05, 0.135, 0.15)
Formula
Frame width ≈ face width at the templesLens width ≈ (frame width − bridge − 2 × 5 mm hinges) ÷ 2Lens size: small < 52 mm, medium 52–55 mm, large 55–58 mm, extra large > 58 mmWorked example
Inputs — Face width at temples: 135 mm; Bridge width: 18 mm; Forehead width: 13 cm; Cheekbone width: 13.5 cm; Jawline width: 12 cm; Face length: 19 cm.
Results — Ideal lens width = 54 mm; Lens size = Medium; Typical temple (arm) length = 142 mm; Estimated face shape = Oval.
Frequently asked questions
What do the numbers on glasses mean?
Lens width, bridge width and temple length in mm – for example 52-18-140.
How do I know if sunglasses are too big?
Your eyes should sit near the centre of the lenses and the frame shouldn't extend far beyond the sides of your face.
Which sunglasses suit a round face?
Angular or rectangular frames that add definition.
What formula does the Sunglasses Size Calculator use?
Frame width ≈ face width at the temples.