By Zencalcy Editorial TeamLast reviewed About us
A compound microscope magnifies in two stages. The objective forms a real, enlarged image in the tube; the eyepiece then acts as a magnifier on that image. Total magnification is the product of those two stages.
Total magnification from tube length and lens focal lengths.
M = (L / f_obj)(D / f_eye)
L is the tube length, D the near-point distance, and f_obj and f_eye the focal lengths. The first factor is the objective's linear magnification, the second the eyepiece's angular magnification.
| Symbol | Meaning |
|---|---|
| M | Total magnification, dimensionless. |
| L | Optical tube length. |
| D | Near-point distance, about 250 mm. |
| f_obj, f_eye | Objective and eyepiece focal lengths. |
M = (160/4) × (250/10) = 40 × 25 = 1000×. Shortening the tube or using a longer eyepiece reduces the total.
Continue with the Mirror Equation Calculator, Mirror Focal Length Calculator, or the Numerical Aperture Calculator — or browse more optics and light tools and all physics calculators.
Only with a high-NA objective and good illumination. Empty magnification beyond the diffraction limit shows a bigger but blurrier image.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026