Each line is an example of newsprint magnified at the given power.  After you print this READING CHART, read it at a distance of 10 to 15 inches from your eyes. Whatever line you read comfortably is the magnification you need for a magnifier. The magnification power is listed to the right.
Reading      10X/40D
Lighting and5X/20D
A magnifier should3X/12D
Allow you to read your mail.2X/8D
This print is similar to small headlines.1.5X/6D
Congratulations! You are now reading small print.