Properly fitted glasses should sit level on your face, rest on your nose without pinching, and stay put when you move your head. The temples (arms) should follow the side of your head with gentle contact and curve down just behind the top of your ears. If your glasses leave red marks, slide down constantly, or give you headaches, something about the fit is off. Here’s how to check every part of the frame.
How the Bridge Should Sit on Your Nose
The bridge is the small arch that connects the two lenses and rests on your nose. It’s the single most important fit point because it bears most of the frame’s weight. On a plastic frame, the bridge should rest flush against both sides of your nose with no gaps. A gap on either side means the bridge is too wide; a gap at the top means it’s too narrow. Either way, the glasses will slide or sit crooked.
Metal frames typically have small adjustable nose pads mounted on thin arms just below the bridge. These pads should sit comfortably on both sides of the nose, distributing weight evenly. When the pads are adjusted correctly, there should be a small visible gap between the lower rim of the frame and your cheeks. If the frame touches your cheeks, the bridge is too wide and the glasses are sitting too low. If that gap is unusually large, the bridge is too narrow and the frame is perched too high.
Bridge widths range from about 14 mm to 24 mm across adult frames. To find your size, check the three numbers printed on the inside of your current frame’s temple arm. The middle number is the bridge width.
Low Bridge Fit: When Standard Frames Slide
Standard frames are designed for noses where the bridge (the bony part between your eyes) sits above the pupils. If your nasal bridge lines up at or below your pupils, or if you have wider facial features or higher cheekbones, standard frames tend to slide down, rest on your cheeks, or sit unevenly.
Low bridge fit frames solve this with a few specific design changes: a wider nose bridge area, larger or more contoured nose pads, more space between the lenses, and a slightly different lens angle. These modifications distribute the frame’s weight more broadly across the nose and keep the glasses from slipping forward. Many brands now label frames as “low bridge fit,” which takes the guesswork out of shopping.
Frame Width and Temple Pressure
The total width of the frame should match the width of your face. You can estimate total frame width by adding the lens width, bridge width, and lens width together (those three numbers printed inside the temple). Lens widths for adults typically range from 40 mm to 60 mm.
When the frame is too narrow, the temples press against the sides of your head. This causes discomfort and can actually push the frame forward off your nose over time. When the frame is too wide, the glasses feel loose and slide forward or tilt to one side. A well-fitted frame makes its first contact with your head just before your ears, not at the temples above them and not squeezing across the whole side of your skull.
Temple Length and the Bend Behind Your Ear
Temple arms range from about 120 mm to 150 mm. The critical measurement isn’t just total length but where the arm bends downward. That bend should happen right at the top of your ear. From there, the remaining piece (called the drop) curves down behind your ear for about 35 mm on an average adult.
If the temples are too short, the bend happens before it reaches your ear, and the glasses won’t stay on securely. If they’re too long, the extra length bunches up behind your ear or sticks out at the back, which feels uncomfortable and looks awkward. Temples that are the right length but poorly adjusted can also cause problems. An optician can heat plastic temples or reshape metal ones to match the exact curve of your ear in a few minutes.
Where Your Eyes Should Sit in the Lenses
Your pupils should be centered horizontally in each lens. Not centered in the frame as a whole, but centered in each individual lens based on your specific pupil distance, since most people’s faces aren’t perfectly symmetrical. This horizontal alignment keeps you looking through the optical sweet spot of the lens rather than through an off-center area that can distort your vision.
Vertically, the math is less intuitive. The optical center of the lens should actually sit about 4 to 5 mm below your pupil center, not directly in front of it. This compensates for the slight forward tilt that frames naturally have when resting on your nose (called pantoscopic tilt). The rule opticians follow is to lower the optical center by 0.5 mm for every degree of tilt. This adjustment is built into your prescription lenses when they’re cut, which is one reason why getting measured in person matters, especially for progressive or bifocal lenses.
Signs Your Glasses Don’t Fit Right
Red marks on the sides of your nose, behind your ears, or across your temples are the most obvious sign that your frames are too tight. Pressure from a poor fit can build throughout the day and lead to headaches or soreness that you might not immediately connect to your glasses.
Even a slight tilt in the frame can throw off the optical alignment of your lenses, causing eyestrain or blurry patches in your vision. If you notice that your vision feels inconsistent, or that you’re tilting your head to see clearly, the lenses may not be positioned correctly in front of your eyes. Poorly adjusted glasses can also affect your posture: you might unconsciously crane your neck forward or tip your chin up to compensate for misaligned lenses, which creates tension headaches of its own.
Frequent sliding is another red flag. If you’re pushing your glasses up multiple times an hour, the bridge is too wide, the temples are too loose, or both. Conversely, if removing your glasses at the end of the day reveals deep indentations behind your ears, the temples are gripping too tightly.
How to Check the Fit at Home
Stand in front of a mirror and look straight ahead. Your glasses should sit level, not tilted to one side. Your pupils should appear roughly centered in each lens from left to right. The top of the frame should follow your brow line or sit just below it, and the bottom of the frame should not touch your cheeks.
Turn your head side to side and nod up and down. The glasses should stay in place without sliding. Now look at the temples: they should run straight back along the side of your head with light, even contact before bending down behind each ear. If one temple presses harder than the other, the frame is probably warped slightly and needs adjustment.
Finally, check the nose area. For plastic frames, run a fingertip along each side of the bridge where it meets your nose. You shouldn’t feel any gaps. For metal frames with nose pads, make sure both pads are contacting your nose evenly and that the frame isn’t resting on your cheeks. Most of these adjustments take an optician only a few minutes and are usually free, even if you bought the glasses elsewhere.