How to Measure an Eyeglass Frame
Your prescription has changed and you need a new pair of eyeglasses.
So you take a little trip down to your local optometrist’s office. You’ve been getting your eyeglasses there ever since your first-grade teacher noticed you were squinting at what she wrote on the blackboard.
You go in and look around. You check out the frames. They’ve got all the cool retro square styles everyone’s wearing. Then you look at a price tag. All of a sudden you have a bad case of sticker shock.
My eyes must be really bad, you think. That can’t say what I think it says. More than $300? Just for the frame?
You ask the optician, who confirms your worst suspicion. Not only that, he gives you a look like he’s saying, if you have to ask how much these glasses cost, you can’t afford them.
That’s it, you say to yourself, after slinking out of there with your hand on your wallet. I’ve had it with these brick-and-mortar eyeglasses stores, where the price gouging feels more like eye gouging. I’m finally going to do it. I’m going to order glasses online, and save all that money I’ve been hearing about.
You’ve just made a decision worth hundreds of dollars. Maybe even thousands in the long run. It’s true. If you shop carefully online, you’ll find prices for discount eyeglass frames and lenses so low you could buy high-quality, stylish eyeglasses for your whole family online for what it would cost to buy just one pair for you locally.
But there’s a major pitfall to avoid when you order glasses online.
How can you make sure the glasses you buy over the internet will fit you if you can’t try them on before you buy them?
That’s a great question. We have an even better answer.
Here is how to make sure the glasses you buy online will fit you well when they come in the mail, and you take them out of the package and try them on.
First, if you already have a pair of eyeglasses that fits you well and looks good on your face, you’re ahead of the game.
All you have to do is get the frame dimensions from these eyeglasses, and order a pair online that matches those dimensions.
It doesn’t even have to be an exact match. All eyeglass frame dimensions are listed in millimeters. A millimeter is a tiny unit of measurement. There are 25.4 millimeters to an inch. So you have a leeway of a few millimeters on each element of a frame.
Those elements are:
The bridge. This is the part of the frame that goes across the bridge of your nose. That’s why it’s called the bridge.
The temple arm. Those are the parts that connect to the front of the frame on either side of your head and rest behind your ear. Sometimes people call the temple arms “legs,” “stems,” or even “bows,” but in the optical industry they’re called temple arms, because they are next to your temple.
The lens width. This is the diameter of one lens, measured at the widest part. It’s also called the “eye size” in the optical industry, which doesn’t make a lot of sense, because it’s not the measurement of the size of your eye; it’s the measurement of the width of your eyeglasses’ lens. We’re mentioning this because sometimes eye doctors will suggest frame dimensions and write these on your prescription. When they do, they may write “eye size” on the prescription when they mean the lens width. So don’t worry about matching that number with the size of your eye. It’s the width of one eyeglass lens.
The lens height. This is measured just like the lens width, but vertically, not horizontally. If your prescription includes an NV-ADD (Near-Vision reading ADDition) number, you can order bifocal or progressive glasses. This is where the lens height measurement becomes crucial: The lens height must be at least 30 millimeters to accommodate a bifocal or progressive prescription.
The frame width. This is the most important measurement on a frame to determine whether it will fit you well and look good on your face. It’s the measurement of the entire front of the frame, from the point that sticks out farthest on the left, to the point that sticks out farthest on the right. Or vice versa.
Remember when we said that if you have a pair of glasses right now that fits you well and looks good on your face you are ahead of the game? Well, you’re rounding third and heading for home if on the inside of one of your temple arms you have three numbers, which are the dimensions of, in order, the lens width, the bridge, and the temple length.
Most of the time, if the numbers are stamped on the inside of the temple arm, they will be listed the way they are in the first example, on the left. (Ignore the first number on the temple arm that precedes these numbers; that will just be the manufacturer’s model or stock number.)
After this model or stock number, the lens width comes first, the bridge is next, and the temple arm is last. Sometimes it could be listed the way it is in the second example, on the right, with the temple arm length first, the lens width next, and the bridge last. Either way, there will usually be a little square between the first and second numbers.
You may even see a pair of glasses that has these numbers stamped or engraved on the inside of the bridge, but this is rare.
If you have the numbers stamped on the inside of the temple arm or on another element of the frame, the only other measurements you need are the frame width and the lens height.
If you don’t have numbers stamped on the inside of the temple arm, you can measure the dimensions of your frame elements with a millimeter ruler. Don’t have a millimeter ruler? Not a problem; you can get one at any drug or dollar store. However, if you have a cloth tape measure with millimeter hash marks, this would be the best measuring tool to use, especially when we come to the temple arm measurement.
Here’s how to measure each element we discussed:
The bridge. Measure horizontally, at the top of the bridge, from the edge of one lens to the edge of the other lens. The part of the frame that holds the lenses in place will be included in the measurement, since you’re measuring from lens edge to lens edge, not frame edge to frame edge.
The temple arm. This is the measurement for which a cloth measuring tape with millimeter hash marks would come in handy. Here’s why: The temple arm is measured from the hinge – where the temple arm connects to the front of the frame – all the way back to the tip.
The measurement includes the bend around the ear, which is why a cloth tape measure is useful for this measurement. If you have a cloth tape measure, you can measure the curve easily. If you’re using a plastic or wood straight-edged ruler, it would be best to do the measurement in two parts.
Start at the hinge, measure to the beginning of the bend, and write that measurement down. Then go back to where you left off, right at the beginning of the bend. Measure the last part, which is angled, to the tip. Add the two sectional measurements together, and that’s the total temple arm length.
You may have a pair of glasses with cable temple arms, the kind that curve around your ear. (pictured above)
If you don’t have a cloth millimeter tape measure, you could print out the downloadable PD ruler at the Zenni Optical website, www.zennioptical.com:
You can use this paper ruler to measure the cable temple arm. Or you could cut a strip of paper about a half-inch wide and 10 inches long. Mark the little paper strip where you begin measuring the temple arm at the hinge. Curve the paper strip around the curve of the temple arm and mark it where the temple arm ends. Stretch out the paper strip and measure the length with a millimeter ruler. That’s your cable temple arm length.
The frame width. Again, it’s the entire horizontal measurement of the front of the frame, measured from the part that extends farthest outward on one side to the part that extends farthest outward on the other side. A metal frame may have a little piece that sticks out on the side toward the top, like the part that extends from the outer edge of the lens on a pair of rimless glasses, just before bending to meet the hinge of the temple arm, such as on this rimless frame:
If you do have a frame such as this one, or any frame with a piece that sticks out on the side, you would include that part of the frame, on each side, in your measurement of the frame width. Whether a frame is too big, too small, or just right for your face is mostly determined by the frame width. Also, make sure you do this measurement at the front of the frame. You don’t need to measure the distance between the two temple arms at the back of the frame.
The lens width. If the width of the frame you are shopping for online matches within two or three millimeters the width of the frame you have that fits you well, you can be confident that the frame you see online will fit you just as well. But be aware of the lens width: even though the total frame width might match the width of your frame, the lens width might be a little narrow or wide for your pupillary distance, which is the measurement of the distance between the middle of each pupil. This measurement determines where to place the optical center on each lens.
The lens height. This is measured just like the lens width, but vertically, not horizontally. Once again, the lens height must be at least 30 millimeters to accommodate a bifocal or progressive prescription. In addition, pay attention to the lens height, because this is an important factor in determining how the glasses will look on your face. If you get a frame with a tall lens height, something over 36 millimeters, the glasses may look too big for your face. Conversely, a too-short lens height, lower than 30 millimeters, may not provide all the corrected-vision coverage your eyes need.
Once you have the measurements of your frame, you can shop for a frame online that will fit you.
Remember, you have a leeway of a few millimeters on each element, with a caveat: Stick to no more than two millimeters higher or lower on the bridge. For example, if your perfect bridge measurement is 18 millimeters, you can go as low as two below that, 16 millimeters, or as high as two above, 20 millimeters. Therefore, a bridge that’s anywhere between 16-20 millimeters should fit you just fine.
Also, if you’re getting a frame with adjustable nose pads, this gives you even more leeway, because the nose pads can be adjusted for the best fit. Pinch them closer together to make the bridge fit more snugly and rest higher on your nose; spread them apart to loosen the fit and let them rest lower on your nose.
On the frame width, lens width, and lens height, you should be fine with a leeway of three millimeters. Therefore, if your perfect frame is 135 millimeters wide, frames between 132-138 millimeters should fit you just as well.
Since many temple arms are adjustable at the curve where the temple arm bends behind your ear, you have a leeway of as many as four millimeters. In that case, if the temple arm on your eyeglasses is 140 millimeters, you will be fine with a temple arm that falls between 136-144 millimeters. However, many temple arms are not adjustable, especially those made of aluminum alloy, titanium, memory titanium, and memory plastic. Check the temple arm material listed in the description of the frame to be sure. Also, look at an enlarged picture of the online glasses. If you can see that embedded in the temple arm is a stainless steel rod, you can be confident that this frame’s temple arm is adjustable.
Here are a few more things to keep in mind. The vintage styles from 50 years ago and more that are popular today were often worn much smaller than glasses are today. This is because lenses were made of glass then, and the heaviness of glass caused eyeglasses manufacturers to keep the lenses as small as possible.
Conversely, eyeglasses in the ’70s were frequently oversized, such as these worn by the late Hollywood super-agent Irving Paul Lazar:
Another thing to keep in mind is how strong your prescription is. If you have a strong prescription, +/- 6.00, the wider and thicker your lenses will be, on the outer edge with a minus sphere (nearsighted) prescription, in the middle with a plus sphere (farsighted) prescription. Therefore, if you have a strong prescription you may want to stick with lens widths that are lower than 50 millimeters.