Diopter indicates the amount of curvature of a lens. The thicker the lens, the bigger the curvature. To find the approximate magnification level of a lens, divide its diopter by 4, and add 1.
The equation is: Magnification = Diopter ÷ 4 + 1
For example: For a 3-diopter lens of a magnifier, its magnification = ¾ + 1 or 0.75 + 1 = 1.75x. Objects viewed under a 3 diopter lens will appear 1.75X larger than normal.
For a 5-diopter lens of a magnifier, its magnification = 5/4 + 1 or 1.25 + 1 = 2.25x. Objects viewed under a 5 diopter lens will appear 2.25X larger than normal.
For a 8-diopter lens of a magnifier, its magnification = 8/4 + 1 or 2 + 1 = 3x. Objects viewed under a 8 diopter lens will appear 3X larger than normal.
Use this chart to convert diopters to magnification simply:
| Diopter | Magnification |
|---|---|
| 2 | 1.5X |
| 3 | 1.75X |
| 4 | 2X |
| 5 | 2.25X |
| 7 | 2.75X |
| 8 | 3X |
| 9 | 3.25X |
| 11 | 3.75X |
| 13 | 4.25X |