Microscope Total Magnification Calculator
Multiply eyepiece, objective and any intermediate lens power to get total microscope magnification, and use the field number to find the field-of-view diameter at that setting.
How it works
Total magnification = eyepiece × objective × intermediate lens · Field of view (mm) = field number ÷ (objective × intermediate lens)
A compound microscope magnifies in stages: the objective forms an enlarged image that the eyepiece magnifies again, and some stands add an intermediate (tube or zoom) lens. Total magnification is simply the product of all three powers. The eyepiece field number, divided by the objective power (and any intermediate factor), gives the real diameter of the specimen you see — higher magnification means a smaller field of view.
Worked example
A 10× eyepiece with a 40× objective and no extra lens gives 10 × 40 = 400× total magnification. With a field number of 20 mm, the field of view is 20 ÷ 40 = 0.5 mm, or 500 µm across.
Sources: Optical microscope — Wikipedia
Frequently asked questions
How do I calculate total magnification?
Multiply the eyepiece (ocular) magnification by the objective magnification, and by any intermediate or zoom lens factor. A 10× eyepiece and 100× oil objective give 1000× total.
Why does the field of view shrink at higher magnification?
The field number is fixed by the eyepiece, and the objective divides it. A higher-power objective spreads a smaller region of the specimen across the same eyepiece field, so you see less area in more detail.
Does the eyepiece affect field of view?
Only through its field number, not its magnification. Field-of-view diameter equals the field number divided by the objective power (times any intermediate lens); a wider-field-number eyepiece shows more at the same magnification.
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Educational estimate, not medical or laboratory advice — verify formulas, units and assumptions for your specific organism or protocol.