Your prescription has changed and you need a new pair of eyeglasses. Instead of paying premium prices at your local optometry office, you decide to shop online—where quality glasses start at much more affordable prices.
If you've never shopped for glasses online before, you'll need to prepare a few key items: an updated prescription, a pupillary distance (PD) measurement, a millimeter ruler, and a current pair of glasses or sunglasses that fit you well.
Your prescription and PD usually come from your eye doctor, but figuring out your frame measurements takes a few extra steps. Don't worry—this guide will walk you through exactly what to measure and how to do it.
What You'll Need Before You Start
| Item | Why You Need It |
|---|---|
| Updated prescription | Ensures your lenses match your current vision needs |
| PD measurement | Positions the optical center of your lenses correctly |
| Millimeter ruler | Essential for accurate frame measurements |
| A well-fitting pair of glasses | Serves as a reference point for size and fit |
How to Measure Each Part of Your Frame
Below are the five key measurements you'll need to find the right frame size. Measure carefully, and don't worry if you're off by a millimeter or two—small variations are normal.
| Measurement | How to Measure | Expert Tip |
|---|---|---|
Frame Width |
Measure horizontally across the front of the frame, from hinge to hinge | This is the overall width of the frame—ensure it matches the width of your face |
Bridge Width |
Measure the distance between the two lenses at the closest point (where the bridge sits on your nose) | Stick within 2mm more or less than your existing measurement for comfort |
Lens Width |
Measure horizontally across one lens, from the left edge to the right edge | Always measure at the widest part of the lens |
Lens Height |
Measure vertically from the top of the lens to the bottom | Measure at the tallest point. For bifocals or progressives, aim for at least 30mm to ensure enough room for all vision zones |
Temple Length |
Measure from the hinge to the bend behind your ear, then from the bend to the end of the arm—add both together | This is the total arm length; most adult sizes range from 135mm to 150mm |
💡 Flexibility tip: Frames with adjustable nose pads give you 2–3mm of leeway, since the pads can be spread apart or pushed together for a custom fit. Temple arms are also adjustable at the curve behind your ear, offering additional flexibility.
No Ruler? Check the Temple or Bridge
Many frames have size numbers stamped or engraved on the inside of the temple arm or the bridge. Look for a series of three numbers—here's how to read them:
Example: 50 18 135
| Number | Meaning |
|---|---|
| 50 | Lens width (in millimeters) |
| 18 | Bridge width (in millimeters) |
| 135 | Temple length (in millimeters) |
⚠️ Note: Some frames display these numbers in reverse order (e.g.,
135 50 18). The key is to identify which number belongs to which measurement—lens width is always the widest of the three, bridge width is the smallest, and temple length is typically the longest.
Frame Features for a Customized Fit
Beyond the basic measurements, you can fine-tune your fit by paying attention to these additional frame features:
| Feature | What It Affects | Why It Matters |
|---|---|---|
| Temple length | How far the arms reach behind your ears | Too short = glasses pull forward; too long = glasses slip down |
| Bridge width | How the frame sits on your nose | Too narrow = pinching; too wide = slipping |
| Lens width | The horizontal size of each lens | Affects both visual field and frame proportion on your face |
| Lens height | The vertical size of each lens | Critical for progressive/bifocal wearers—needs at least 30mm |
When shopping online, use the filter options to narrow down frames by these measurements. This saves time and helps you avoid frames that simply won't fit
Frequently Asked Questions
Q: Do I need to measure my current glasses exactly?
A: Close counts. If you're within 1–2mm of your current pair's measurements, the new frames should fit similarly—especially if they have adjustable nose pads or spring hinges.
Q: What if my current glasses don't fit well?
A: That's a great opportunity to improve your fit. Note what's uncomfortable (too tight? slipping?) and adjust your target measurements accordingly—slightly wider bridge, longer temples, etc.
Q: Can I use a standard ruler instead of a millimeter ruler?
A: You can, but millimeters are more precise. Most rulers have millimeter markings on one side—use that side. Eyeglass measurements are always in millimeters.
Q: What's the most important measurement for online shopping?
A: Frame width and bridge width are the most critical for comfort. Lens height matters most for progressive lens wearers. All five measurements work together, but start with the bridge—if that doesn't fit, nothing else will feel right.
Q: How do I know if a frame will be too big or too small for my face?
A: A general rule: your frame width should be roughly the same as your face width at the temples. Frames that are too narrow will pinch; frames that are too wide will slide down and look oversized.
Disclaimer: This content is for informational and marketing purposes only and does not constitute professional medical or optical advice. Always consult a licensed optometrist for personalized vision care recommendations.
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