The first number is the glasses’ lens width, the second is the glasses’ bridge width, and the third is the glasses’ temple-arm length. If your glasses don’t have this information printed, you’ll need to find those measurements with a ruler.
In most pairs of glasses, the lens width can vary between 35–60 millimetres (1. 4–2. 4 in). Although the lenses themselves are convex, you do not need to add any extra length to the lens measurements to compensate for the curved lens.
Generally speaking, the lens height measurements range from 21–45 millimetres (0. 83–1. 77 in). If you’re hoping to get bifocals or progressive lenses, you’ll need to have a lens height of at least 30 millimetres (1. 2 in).
Measuring the glasses in this way will give you the frame width. Frame width measurements can vary between 110–150 millimetres (4. 3–5. 9 in).
When purchasing new glasses, it’s important that you measure the bridge width as accurately as possible. Try to be accurate to within 2 millimetres (0. 079 in). This is important since the glasses won’t fit on your face if the bridge measurement is off. Bridge measurements typically only vary between 5–25 millimetres (0. 20–0. 98 in).
Depending on the size of your glasses, the temple arm measurement can vary from 118–150 millimetres (4. 6–5. 9 in). If you find that it’s too challenging to measure around the bend in the arms, try measuring the arm in 2 different measurements. Measure from the hinge to the center of the bend and then measure from the end of the arm to the center of the bend. Add the 2 numbers together to get the full arm length.
