How to Measure an Eyeglass Frame

  • BY Zenni Optical

Your prescription has changed and you need a new pair of eyeglasses. This time you decide to buy them online instead of in the store. If you’ve never shopped for glasses online,  you’ll need to prep yourself with a few crucial measurements: an updated prescription, a pupillary distance (PD) measurement,  and frame size. Your prescription and PD will usually come from your eye doctor (or you can learn to measure your own PD here), but figuring out your frame size will take a few extra steps. Not to worry –  we are going to take some time to share tips and tools that will help you find the perfect fitting frame. 

Measure Your Frame Width

If you already have a pair of eyeglasses that fits you well, you’re ahead of the game.  All you have to do is use a millimeter ruler to measure the frame width– 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. Zenni has specific measurements for kids and adults frames. The average adult frame width is 136-138mm and kids frame width is 125-127mm.  If you are starting from scratch and don’t have a good fitting pair of glasses, then we have a great frame cut out tool that you can use from the comfort of your home. All you need to do is download, print, cut out the frame sizes, and hold up to your face to determine which fits best. Once your frame width has been determined, you can shop at Zenni while filtering by the correct size. Take a look at our adult and kid frame-cut outs here

Extra Frame Customization

In addition to the frame width, you can get a more tailored fit through the temple length (the parts that connect to the front of the frame on either side of your head and rest behind your ear), and the  bridge width (the part of the frame that goes across the bridge of your nose), and lens width  (the diameter of one lens, measured at the widest part). An average temple width is 135-140mm, average bridge width is 18-20mm, and average lens width is 54 mm.

The Box System

Another way to measure  frames is with the  “box system,” which uses lens width, bridge width, and temple length. Although Zenni doesn’t use the box system on all our frames, you may have noticed frames with numbers marked on the temples with the bridge and lens width separated by a box symbol, as below: 

These numbers may also be  stamped or engraved on the inside of the bridge.


Here’s how to measure each part of the frame:

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.

Temple arm– this part is measured from the hinge – where the temple arm connects to the front of the frame – all the way back to the tip.

Lens width–  the width at the widest part of the lens, from right inside of one lens edge to the other.

Remember, you have leeway of a couple millimeters for each frame part., If you’re getting a frame with adjustable nose pads, this gives you even more leeway because the nose pads can be adjusted closer or wider for the best fit. Since many temple arms are adjustable at the curve where the temple arm bends behind your ear, you have a leeway of a few  millimeters there too. 

Now that you have all your frame measurements sorted, head to Zenni to shop for the perfect frame to fit your face!