There is a big difference in the cost of stock spectacle lenses and special grind lenses. You can therefore save money by using stock lenses when they will be suitable for a particular frame. You can also save frustration by not ordering stock lenses when they will be impossible for the selected frame.
This website of optometry resources includes a worksheet to calculate the minimum lens blank size for the patient’s PD and the dimensions of the frame selected. You can use the result to make sure that the ordered lenses will be big enough, but not too big and therefore needlessly thick.
TIP: Print copies of the worksheet on A4 paper, then use these to make the calculation. Keep this sheet until the ordered lenses are returned in case there are any questions from the lens laboratory or your fitting lab.
Click here to go to the page: Then scroll to >Dispensing Aids
Click here to view the download.