There are three basic components to frame sizing: the A, the DBL, and the temple.

You will need to know the “size” of a frame when ordering it from the manufacturer. You will also need to be able to measure a frame in order to provide information to the lab for lens orders.

For “size,” virtually every frame will have two numbers stamped or painted on or near the bridge (or they may be found on the temple). In the United States, eyeglass frames are measured using the boxing system, which uses those two numbers to express a frame size.

The Boxing System:
The frame A is the longest horizontal opening in the eyewire.
The frame DBL is the closest measurement between the two lenses.
The ED is the effective diameter of the eyewire opening which is used in determining lens cut-out in finishing work.
The B is the longest vertical opening in the eyewire.

Note: A bridge size and the DBL are not the same measurement. When a bridge size is expressed, it is the distance between the lenses at one half the “B” measurement. When a DBL size is expressed, it is the closest distance between the lenses regardless of where it occurs. 

Regarding frame sizes, just think, “the larger the numbers, the larger the frame.” A large man’s frame may have a boxing system size of 62 20, while a child’s frame may have a boxing system size of 40 16.

For adult frames, most “A” measurements will fall between 60 and 49 for men and between 53 and 49 for women.

For children’s frames, most “A” measurements will fall between 40 and 45.

In today’s adult frames, most DBL (distance between lenses) measurements will fall between 13 and 21 for men and women and between 17 and 19 for children.

The DBL measurement is related to the “A.” As “A” increases, the DBL may remain the same or it may increase by one or two millimeters.

When you speak with a lab or a frame company, you will often express the “A” measurement as the “eye-size,” or simply the “eye,” as in, “I need a Sarah Woo Model 9876 in a 46 eye.”

Note: The frame A and frame DBL added together provide the frame PD (pupillary distance): A + DBL = Frame PD. The frame PD is used in laboratory finishing to calculate lens decentration (the displacement of the lens OC to match the patient PD, see Lesson 6). Example: A frame with an A of 58 and a DBL of 16 has a frame PD of 74. This also represents the geometric opening of the frame eyewires.

The third component in frame size is the temple length. The standard temple length for an adult frame is 140 mm. Temples will run from 130 – 145 mm on standard adult frames and from 120 – 140 on children’s frames. In general, temple length will increase as the A and DBL increase. Most frames will only come with one temple size, but you can always call the manufacturer to check on the availability of other sizes. Many manufacturers will provide “custom” lengths with some three-piece mountings even offering 135, 140, 150, 160 and a special order 170 mm size.

“BIG-GUY” frames may come with 145, 150, 155 or 160 temples.

When a prescription calls for a progressive lens, you will also have to provide a “B” measurement to the lab for lens fabrication. The “B” measurement is the longest vertical measurement in the eyewire opening.

All other measurements involving frames are only used in the finishing lab when laying out lenses to be cut for a particular frame. The numbers indicated on the frame are for reference only and are not to be used for lab work. For any lab work, always use a PD stick and manually measure frames for A, B and DBL.