DIOPTER VS MAGNIFICATION GUIDE This is considered the archery standard. However it does not reflect actual magnification.  Advertised Powers and Diopters may vary between MFG's. Below are calculators that will give your actual magnification based on your specifications. Note all input and output is in inches / decimal inches.   Diopter  Magnification  .25  2x  .375  3x  .5  4x  .625  5x  .75  6x  .875  7x  1  8x Apparent Magnification Fill-in two out of the three fields, hit the calculate button, and the form will figure out the missing value for you.   Apparent magnification:   Diopter:   Distance eye to sight inches:   Leave one field above blank then press calculate.   Coverage Given Dot Size Fill-in all fields, hit calculate, and the form will figure out unmagnified and magnified coverage values.   Dot size inches:   Yards to target :   Distance eye to sight inches:   Apparent magnification:     Unmagnified coverage:   Magnified coverage:     Dot Size Given Coverage Fill-in all fields, hit calculate, and the form will figure out dot size and dot sized magnified.   Distance eye to sight inches:   Area to cover unmagnified:   Yards to target:   Apparent magnification:     Dot size required:   Dot size required magnified: