The best way to determine which strength of reading glasses is right for you is to visit an optometrist. A complete vision exam will give you a clear prescription number that will work for you.  You can also simply try on different pairs of reading glasses, and use the arm’s length test. Hold reading material at an arm’s length, a comfortable distance for reading, and see which strength offers you clear vision. Once you find the pair that suits you best, check the inside of the temple arm or lens for the diopter number, which indicates the level of magnification. This number ranges from +1.00 to +4.00 in increments of +0.25.