By Zencalcy Editorial TeamLast reviewed About us
A magnifying glass does not make an object physically larger; it lets your eye get closer while still focusing. The angular magnification depends on the lens focal length and on whether the image is placed at the near point or at infinity.
Angular magnification of a simple magnifier.
Near point: M = 1 + D / f Relaxed: M = D / f
D is the near-point distance, conventionally 250 mm, and f is the focal length. The near-point form gives the larger magnification but demands more accommodation.
| Symbol | Meaning |
|---|---|
| M | Angular magnification. |
| D | Near-point distance, about 250 mm. |
| f | Focal length of the magnifier. |
At the near point, M = 1 + 250/50 = 6×. With the eye relaxed, M = 250/50 = 5×. A shorter focal length magnifies more but has a smaller usable eye distance.
Continue with the Malus's Law Calculator, Microscope Magnification Calculator, or the Mirror Equation Calculator — or browse more optics and light tools and all physics calculators.
Higher ratings need very short focal lengths, which force the eye close to the lens and reduce the field of view. Practical loupes rarely exceed 10×.
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.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026