Eyeglass frame size chart

The three numbers inside a temple arm, like 52 □ 18 – 140, are the lens width, the bridge and the temple length in mm (ISO 8624). A 52-18 front is about 134 mm across, a medium frame. Lay your glasses lenses-down on the 1:1 outline to read a frame whose print has worn off.

Try

Lay your glasses lenses down on the screen and adjust lens width, height and bridge until the outline matches.

52 □ 18 – 140about 134 mm across · span shown 134 mm

Lens width52.0 mm

Lens height40.0 mm

Bridge18.0 mm

Temple

Full chart 10 rows

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Frame size by lens and bridge

10 rows

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Eyeglass lens widths 44 to 62 mm with lens size band and estimated total frame width for 16, 18 and 20 mm bridges

Small lens	≈ 116 mm	≈ 118 mm	≈ 120 mm	Narrow (under 130 mm)
Small lens	≈ 120 mm	≈ 122 mm	≈ 124 mm	Narrow (under 130 mm)
Small lens	≈ 124 mm	≈ 126 mm	≈ 128 mm	Narrow (under 130 mm)
Medium lens	≈ 128 mm	≈ 130 mm	≈ 132 mm	Medium (130–137 mm)
Medium lens	≈ 132 mm	≈ 134 mm	≈ 136 mm	Medium (130–137 mm)
Medium lens	≈ 136 mm	≈ 138 mm	≈ 140 mm	Wide (over 137 mm)
Medium lens	≈ 140 mm	≈ 142 mm	≈ 144 mm	Wide (over 137 mm)
Medium lens	≈ 144 mm	≈ 146 mm	≈ 148 mm	Wide (over 137 mm)
Medium lens	≈ 148 mm	≈ 150 mm	≈ 152 mm	Wide (over 137 mm)
Large lens	≈ 152 mm	≈ 154 mm	≈ 156 mm	Wide (over 137 mm)

05 / Field guide

Three numbers
on the arm.

Most frames carry their size printed inside a temple arm, like 52 □ 18 – 140. Once you know what the three numbers mean you can buy a new pair that fits like your old one, and if the print has worn away, you can measure the front at true size on this page.

What 52 □ 18 – 140 means

The marking follows ISO 8624, the boxed lens system. Imagine a rectangle drawn around each lens: the first number is the width of that box in millimetres, the lens width. The square symbol stands for the box. The second number is the bridge, the shortest distance between the two lenses. The third is the temple length, from the hinge screw to the tip of the arm, measured along it including the bend.

Sometimes a fourth number gives the lens height. Progressive and bifocal lenses need about 28 mm or more of height so there is room for the reading zone.

Front width ≈ 2 × lens + bridge + hinges (about 6 mm each side)

Total width is not printed

The overall width across the front is what sets whether a frame looks wide or narrow on your face, and it is not part of the marking. A 52-18 front is about 134 mm across including the hinges. Sellers group frames by it: one widely used banding is narrow under 130 mm, medium 130–137 mm and wide above 137 mm.

Lens width is grouped too: about 49 mm or less is small, 50–60 mm medium and above 60 mm large. Two frames can share a total width with different numbers, such as 54-16 and 52-20, and fit the nose differently because the bridge differs.

Measuring a frame on screen

Lay the glasses lenses-down on the calibrated stage and adjust lens width, height and bridge until the outline matches. On a phone, half the front is drawn from the centre of the bridge, so line the middle of the bridge up with the red centre line. The temple arm curves, so read its length from the print or measure it along the arm with a tape.

Wraparound sunglasses with a strong curve do not lie flat, so on-screen widths read short. For those, rely on the printed numbers.

How close is close enough

A frame within about 2 mm of lens width and 1 mm of bridge usually fits the same. Temple lengths come in 5 mm steps; if your current pair slips or pinches behind the ears, go up or down one step.

Questions

Answered plainly.

01What do the numbers on glasses mean?+

Lens width, bridge and temple length in millimetres. In 52 □ 18 – 140, each lens is 52 mm wide, the bridge 18 mm and the arms 140 mm long.

02What is a medium frame size?+

By total width, about 130 to 137 mm; by lens width, about 50 to 60 mm. A 52-18 frame is about 134 mm across, a medium.

03How do I measure my glasses frame width?+

Measure straight across the front from hinge to hinge, or lay the glasses on the calibrated 1:1 outline. It is roughly two lens widths plus the bridge plus about 12 mm.

04What bridge size do I need?+

Use the bridge of a pair that sits comfortably. Within 1 mm feels the same; a narrow bridge sits higher on the nose, a wide one lower.

05What lens height do I need for progressives?+

Most progressive lenses need about 28 mm of lens height or more, so there is room for the distance, intermediate and reading zones.

06Can I measure sunglasses on the screen?+

Flat-fronted ones, yes. Strongly curved wraparound sunglasses do not lie flat, so use their printed size instead.