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How much can a compound light microscope magnify an object?

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microscope Colour-enhanced scanning electron micrograph (magnified 50×) of a bean aphid on a leaf.

The magnifying power of a compound microscope is determined by the product of the magnification of the objective lens and the eyepiece. While there is no theoretical limit to the amount of magnification possible in an optical system, practical magnification is constrained by the system's resolving power—its ability to form distinguishable images of objects separated by small distances.12

The maximum useful magnification for a compound microscope typically ranges from 100× to 1,500×, depending on the objective lens used.3

| Objective Focal Length (mm) | Numerical Aperture (N.A.) | Maximum Useful Magnification |
| :--- | :--- | :--- |
| 32 | 0.10 | 100× |
| 16 | 0.25 | 250× |
| 8 | 0.50 | 500× |
| 4 | 0.95 | 1,000× |
| 3 | 1.38 | 1,500× (oil immersion) |

As shown in the table, higher magnification is achieved by increasing the numerical aperture of the objective lens, often through the use of immersion objectives that utilize liquids to improve resolution.43