The right frame size is the one whose total width matches the width of your face, whose bridge sits on your nose without pinching or sliding, and whose temples reach your ears without pressing. The quickest way to find it is to read the three numbers printed inside a pair you already own, then shop frames within a few millimetres of those values. This guide explains what the numbers mean, how to measure without them, and how IGIOO's S, M and L sizes map to real faces.
The three numbers inside your glasses
Look at the inside of the temple arm (the part that goes over your ear) on a pair of glasses you already have. You will usually see something like 52 □ 18 140. Those numbers describe the frame size in millimetres:
- Lens width (52): the horizontal width of one lens at its widest point.
- Bridge width (18): the distance between the two lenses, where the frame rests on your nose.
- Temple length (140): the length of the arm from the hinge to the tip behind your ear.
Some frames add a fourth number for lens height, which matters for progressive and bifocal lenses. If a pair fits you well today, write these numbers down. They are your starting point for every online order.
Frame width is the number that matters most
Lens width alone can mislead you, because a thick acetate frame and a thin metal frame with the same lens width look very different on the face. What you really want to match is the total frame width, measured from the outer edge of one lens rim to the other. As a rule of thumb, it is roughly two lens widths plus the bridge plus the thickness of the rims.
A good fit looks like this from the front:
- The frame is about as wide as your face at the temples, give or take a few millimetres. Your eyes sit close to the centre of each lens.
- Your eyebrows are visible just above the top edge of the frame, not hidden behind it.
- Your cheeks do not push the frame up when you smile.
If a frame is too narrow, the temples splay outward and leave red marks. If it is too wide, the glasses slide down and your eyes look crowded toward the bridge. Our frame size measurement guide shows each dimension on a diagram if you prefer a visual reference.
How to measure your face without an old pair
No glasses to copy from? Stand in front of a mirror with a ruler marked in millimetres and take two readings:
- Face width. Hold the ruler horizontally just below your eyes and measure from one temple to the other, where the arms of the glasses would rest. Most adults land somewhere between 125 and 145 mm.
- Bridge check. Look at where your nose meets your face. A high, narrow bridge usually suits a smaller bridge measurement; a low or wide bridge suits a larger one, or a frame with adjustable nose pads.
A frame whose total width is within about 3 mm of your face width will usually sit comfortably. Hinges and temples have some flex, so you do not need an exact match. For a complete fit you will also need your pupillary distance, which positions the optical centre of each lens in front of your pupil. It only takes a minute to measure at home.
IGIOO sizes: S, M and L in practice
Every frame at IGIOO is tagged S, M or L, and the size is listed in the product description. The letters describe the total frame width, so you can filter quickly and then confirm the details on the product page.
| Size | Who it usually suits | Typical signs you need it |
|---|---|---|
| S (small) | Narrower faces, petite features, many teenagers and adults with a slim face | Standard frames slide down or look too wide; eyes sit close to the bridge |
| M (medium) | The majority of adult faces | Most frames you have owned fit without adjustment |
| L (large) | Wider faces, prominent cheekbones, anyone who prefers bigger lenses | Medium frames pinch at the temples or leave marks behind the ears |
Here is one frame from each size so you can see how the proportions change:
Malcolm is a lightweight TR square frame in size S that suits narrower faces. Dominic is a full-rim acetate frame in size M with a slightly squared outline, offered in Tortoise and Black. Kaylen is a solid acetate rectangle sized L for wider faces or anyone who likes a bigger lens.
Bridge fit: the detail most people skip
Two frames with identical width can fit completely differently because of the bridge. The bridge decides where the frame sits on your nose, which in turn decides whether the lenses are centred on your eyes and whether the frame touches your cheeks.
- Acetate and TR frames have a fixed bridge moulded into the front. Choose the bridge number carefully, because it cannot be widened much. A keyhole bridge spreads the weight over a wider area and often suits a lower nose bridge.
- Metal and mixed-material frames usually have adjustable nose pads. These can be bent slightly inward or outward, so they forgive a bridge number that is a millimetre or two off.
If your glasses always leave marks on your nose or slide down when you look at your phone, the bridge is the first thing to change, not the lens width.
Temple length and lens height
Temple length matters less than width because the arms bend at the tip and can be adjusted. Most adult frames come with temples between 135 and 150 mm, and the common lengths fit most heads. If you have a larger head or wear your glasses low, a longer temple keeps the tips behind your ears instead of on top of them.
Lens height becomes important when you order progressive lenses. The lens needs enough vertical room for the distance zone at the top and the reading zone at the bottom. Very shallow, narrow frames can make the reading area feel small, so for progressives lean toward a frame with a taller lens. For single-vision lenses, lens height is mostly a question of style.
Size and face shape work together
Size tells you whether the frame fits; shape tells you whether it flatters. A round face often looks balanced in a rectangle or square frame, a square face is softened by round or oval lenses, and an oval face can wear most shapes. Our frame and face shape guide goes through each face shape in detail. Pick the shape first, then use the S, M and L tags to find that shape in your size. The square and rectangle collections, for example, each span all three sizes.
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Frequently asked questions
What if my old glasses have no numbers printed inside?
Lay them on a table and measure with a millimetre ruler: one lens edge to edge for lens width, the gap between the lenses for the bridge, and hinge to tip for temple length. Measuring the whole front from end to end gives you total frame width, which is the most useful number to shop by.
How close does the new frame need to be to my old measurements?
Within about 3 to 5 mm of total width is usually fine, because temples flex and nose pads can be adjusted. Keep the bridge closer to your old number on acetate or TR frames, since a moulded bridge cannot be reshaped.
Do sunglasses follow the same sizing?
Yes. Sunglasses use the same lens, bridge and temple measurements, though many styles run larger for extra coverage. If you normally wear size M eyeglasses, a size M sunglasses frame will sit the same way on your face.
Can I order progressive lenses in a small frame?
You can, but a taller lens gives the reading zone more room. If you are set on a small frame, look for one with a bit more lens height, and add your prescription with the ADD value in the lens selector.
What if the frame arrives and does not fit?
Every IGIOO frame is covered by our 14-day fit and style guarantee. Check the returns and exchange page for the simple steps to swap for a different size.
Find your size in our eyeglasses collection
Browse all eyeglasses and use the S, M and L tags to narrow the list to frames that will sit comfortably on your face, then choose the shape and colour you love. Add your prescription in a few clicks with our lens selector.
