Where to Find Your Frame Size
Every manufactured eyeglass frame has its measurements printed on the inside of the temple arm (the part that folds against the lens). This marking is required by the Frame Manufacturer's Marking Standard and is present on virtually all prescription eyewear.
The Format Explained
Look at the inside of either temple arm — usually the left one. You will see three numbers in a specific format:
| Example Size | 50 | □ | 18 | 140 |
|---|---|---|---|---|
| Measurement | Lens Width (mm) | Box symbol | Bridge Width (mm) | Temple Length (mm) |
The box symbol (□) separates the lens width from the bridge width. The temple length follows after a space. You may also see additional markings nearby — such as a brand name, model number, or country of origin — but the three core numbers are always there.
Other Places Measurements Appear
- On a sticker: New frames often have a sticker on the lens or frame with the size printed on it. This sticker may be removed after purchase.
- On the original packaging: The measurements are typically printed on the box or hang tag that comes with the frame.
- On the nose pads: Some metal frames have measurements stamped or engraved on the bridge or nose pad components.
The Three Measurements Explained
1. Lens Width (□)
Lens width is the horizontal distance across one lens, measured at its widest point from the temporal (outer) edge to the nasal (inner) edge. This is the most important measurement because it determines how much of your field of vision the lens covers and how the frame sits on your face.
Lens width ranges from approximately 38mm to 62mm in standard frames. The most common sizes are 48mm, 50mm, 52mm, and 54mm.
2. Bridge Width
Bridge width is the distance between the two lenses — the space across the bridge of your nose. It is measured at the narrowest point between the lenses where they meet the nose pads or frame bridge.
Bridge width ranges from approximately 14mm to 24mm. If the bridge is too narrow, the frame will pinch the nose. If it is too wide, the frame will slide down the nose or sit crookedly.
3. Temple Length
Temple length is the length of the temple arm from the hinge (where it attaches to the front of the frame) to the tip. It is measured along the outside of the arm, not along the curve.
Temple length ranges from approximately 120mm to 155mm. Most adults need 130mm to 145mm. A temple that is too short will not reach your ear; one that is too long will extend too far past your ear and may be uncomfortable.
Total frame width — the overall horizontal width of the front of the frame — is not printed on the frame but can be calculated: lens width × 2 + bridge width = total frame width. For example, 50mm + 50mm + 18mm = 118mm total frame width.
Standard Size Ranges by Category
The following table shows typical measurement ranges for different categories of eyeglass wearers.
| Category | Lens Width | Bridge Width | Temple Length | Total Frame Width |
|---|---|---|---|---|
| Children (ages 3–7) | 40–46mm | 13–16mm | 110–125mm | 95–110mm |
| Children (ages 8–12) | 44–48mm | 14–17mm | 120–130mm | 105–118mm |
| Teenagers | 46–52mm | 15–18mm | 125–135mm | 110–125mm |
| Women (small face) | 44–50mm | 14–18mm | 130–140mm | 105–120mm |
| Women (average face) | 48–54mm | 16–19mm | 135–145mm | 115–130mm |
| Men (small face) | 46–52mm | 15–18mm | 130–140mm | 110–124mm |
| Men (average face) | 50–56mm | 17–20mm | 135–145mm | 120–135mm |
| Men (large face / oversized) | 54–62mm | 18–24mm | 140–155mm | 130–150mm |
How to Measure Your Current Glasses
If you have a pair of glasses that fits you well, you can use them to find your exact frame size. This is the most reliable method because it captures the fit you already know works for you.
Tools needed: A millimeter ruler, a printed ruler app on your phone, or digital calipers. Digital calipers are the most accurate and are available online for $10–$20.
Step-by-Step Instructions
Step 1: Measure Lens Width
Place the glasses lens-side down on a flat surface. Measure one lens at its widest horizontal point — from the outer (temporal) edge to the inner (nasal) edge where it meets the frame rim. Do not include the frame itself. The average lens width for an adult is 46–56mm. Both lenses should measure within 0.5mm of each other.
Step 2: Measure Bridge Width
With the glasses still lens-side down, measure the bridge — the narrowest part that connects the two lenses. Place your ruler at the point where the inner edge of the left lens meets the bridge, and measure straight across to the inner edge of the right lens. This is the bridge width.
Step 3: Measure Temple Length
Open one temple arm and lay it flat on the ruler. Start measuring from the hinge (the point where the temple attaches to the frame front) and measure to the tip of the temple arm. Most temples are between 125mm and 150mm long. Both temples should be within 2mm of each other.
Step 4: Record Your Size
Combine the three numbers in the standard format: Lens Width □ Bridge Width Temple Length. For example: 52□17 140.
HowTo Schema Summary
| Step | What to Measure | Where | Typical Result |
|---|---|---|---|
| Step 1 | Lens Width | Widest point of one lens, inner to outer edge | 46–56mm |
| Step 2 | Bridge Width | Narrowest point between the two lenses | 14–22mm |
| Step 3 | Temple Length | Hinge to temple tip along the outside | 125–150mm |
| Step 4 | Full Size | Combine: Lens Width □ Bridge Width Temple Length | e.g., 52□17 140 |
How to Measure Your Face for Glasses
If you do not have a well-fitting pair of glasses to measure, you can measure your face directly. This is less precise than measuring an existing frame but is a useful starting point for finding your size online.
What to Measure
Face width (temple-to-temple): Stand in front of a mirror or have someone help you. Use a soft measuring tape or a strip of paper. Wrap it around your face at the level of your temples — the widest part of your face, roughly at the same height as the upper edge of your ears. This measurement corresponds to the total frame width. Subtract 10–14mm to estimate the frame's lens width + bridge width.
Nose bridge width: Use a ruler to measure the width of your nose bridge — the flat area between your eyes where the glasses will sit. Place the ruler across the widest part of your nose bridge and measure from one side to the other. This helps you determine whether you need a narrow, medium, or wide bridge.
Temple-to-ear length: Measure from your temple (where the frame would sit) to the top of your ear — the point where the temple arm would rest. This helps determine temple length. Subtract about 20mm from this measurement because the temple arm starts at the frame front, not at your face.
Face Measurements to Frame Size Estimates
| Total Face Width | Estimated Total Frame Width | Estimated Lens Width + Bridge | Typical Category |
|---|---|---|---|
| 110–120mm | 115–125mm | 44–48mm lens + 14–16mm bridge | Narrow / small face |
| 120–132mm | 125–138mm | 48–52mm lens + 15–18mm bridge | Medium / average face |
| 132–145mm | 138–152mm | 52–56mm lens + 17–20mm bridge | Wide / large face |
| 145–160mm | 150–165mm | 56–60mm lens + 19–22mm bridge | Extra wide / oversize |
Frame Size and Face Shape Matching Rules
Frame size is not just about comfort — it also affects how your glasses look on your face. The right size balances proportion with style.
| Face Shape | Recommended Frame Width | Recommended Lens Width | Style Tips |
|---|---|---|---|
| Round face | Frames slightly wider than the face | 52–56mm | Angular frames add definition. Avoid perfectly round frames. |
| Square face | Frames as wide or slightly wider than the jaw | 50–56mm | Round or oval frames soften angular features. Avoid boxy square frames. |
| Heart-shaped face | Frames slightly wider than forehead | 48–54mm | Bottom-heavy frames or semi-rimless styles balance a wider forehead. |
| Oval face | Frames proportional to face width | 48–54mm | Most frame shapes work. Avoid frames that cover more than half your face. |
| Long/oval face | Frames wider than the face | 50–56mm | Deep lenses (taller frame) balance a long face. Avoid narrow frames. |
| Diamond face | Frames as wide as the cheekbones | 46–52mm | Cat-eye or oval frames highlight cheekbones and soften narrow temples. |
Proportion rule: A frame should extend about 3–5mm beyond the widest part of your face on each side. If the frame is too narrow, it will squeeze your face. If it is too wide, it will look out of proportion and may not stay in place.
Using Size Filters When Shopping Online
One of the biggest advantages of buying glasses online is the ability to filter frames by exact measurements. Most major online retailers include size filters in their search results.
How to use size filters:
- Enter your lens width (e.g., 50mm) as the first filter value
- Enter your bridge width (e.g., 18mm) as the second filter value
- Enter your temple length (e.g., 140mm) as the third filter value
Some retailers allow you to filter by total frame width instead of or in addition to individual measurements. The total frame width is the single most important measurement for fit — it tells you whether the frame will be too narrow or too wide for your face.
Major Retailers with Size Filters
| Retailer | Size Filter Available? | Filter Format | Notes |
|---|---|---|---|
| Warby Parker | Yes | Lens width + Bridge + Temple | Also filters by total frame width; very intuitive interface |
| Zenni Optical | Yes | Lens width, Bridge, Temple — separate fields | Free exchange if size does not fit |
| EyeBuyDirect | Yes | Lens width + Bridge + Temple | Also allows filtering by face shape and frame width |
| Coastal.com | Yes | Size range (S/M/L/XL) + exact measurements | Advanced search with multiple measurement fields |
| LensCrafters (online) | Yes | Lens width + Bridge + Temple | Includes virtual try-on tool |
| GlassesUSA | Yes | Frame width + Lens width + Bridge | Also filters by frame material, shape, and size category |
Tolerance note: You do not need an exact match. A ±2mm variance in lens width and bridge width is generally well-tolerated and should not cause fit problems. Temple length can vary by ±5mm without issue. If you are between sizes, start with the smaller size — it is easier to adjust small frames to fit slightly wider than the other way around.
What Happens If the Frame Size Is Wrong
Wearing glasses with incorrect measurements is uncomfortable and can cause real problems. Here is what can go wrong:
| Problem | Cause | Symptoms | Solution |
|---|---|---|---|
| Frames too narrow | Lens width + bridge too small for face | Temples press on temples; red marks; frame sits crooked; headaches | Return and exchange for wider frames |
| Frames too wide | Lens width + bridge too large for face | Glasses slide down nose; image distortion; temples feel loose | Adjust temples inward or exchange for narrower frames |
| Bridge too narrow | Bridge width smaller than nose width | Nose pinching; red marks on nose; frame lifts off face | Nose pad adjustment or different frame with wider bridge |
| Bridge too wide | Bridge width larger than nose width | Frame slides down; gaps between nose and frame | Nose pad adjustment or different frame |
| Temples too short | Temple length too short | Glasses feel unstable; temples do not reach ears; frame lifts with movement | Return and exchange for longer temples |
| Temples too long | Temple length too long | Temples extend past ears; discomfort behind ears; poor retention | Optician can shorten temples slightly by bending |
| PD mismatch (not a frame issue, but related) | Optical center of lens not aligned with pupil | Eye strain; headaches; blurry vision; double vision at edges | Verify your PD with an optician; re-order with correct PD |
Many fit issues can be corrected by an optician — temples can be bent slightly inward or outward, nose pads can be adjusted, and in some cases temples can be trimmed. However, if the total frame width or bridge width is significantly off, an optician cannot fix it and you will need a different frame.
PD and Frame Size: How They Work Together
Pupillary distance (PD) and frame size are related but distinct measurements. Your PD must align with the optical center of your lenses, which is determined by the frame's lens width and how the frame sits on your face.
If you have a narrow PD (under 60mm) and order glasses with very large frames (lens width 56mm+), the optical center of each lens will be too far apart to match your pupils. This causes prismatic effects — double vision, eye strain, and headaches.
Similarly, a wide PD (over 68mm) in small frames will push the optical centers too close together.
General guideline: Your lens width should be roughly half your PD, plus 2–4mm of additional coverage on each side. For example, if your PD is 63mm, your ideal lens width is approximately 30–32mm per lens. Standard 52mm lenses in a frame with an 18mm bridge would result in a total frame width of 122mm, which may work for this PD, but you should verify with your optician or use an online PD calculator.
Summary: Getting the Right Frame Size Every Time
Finding the right frame size is a three-step process:
- Find your current size: If you have glasses that fit well, measure them or look for the numbers printed on the temple arm. Record them in the format: Lens Width □ Bridge Width Temple Length.
- Know your face width: Measure your face or use your current glasses' total frame width (lens width × 2 + bridge width) as a reference. Online retailers use this to recommend sizes.
- Use size filters: When shopping online, enter your exact measurements into the size filter. Start with exact matches and relax to ±2mm if no exact options exist. Check the total frame width against your face width.
Getting the right frame size eliminates the most common cause of online glasses fit problems. Most reputable online retailers offer free exchanges if the size is not right — so there is little risk in buying online once you know your numbers.