Total Magnification Calculator
Enter the objective-lens power and the eyepiece power to get the total magnification of a compound light microscope — and see why the two stages multiply instead of add.
Two lenses, one number
Enter the objective and eyepiece magnifications and the calculator returns the total magnification — the product of the two stages.
Read the lens labels
Use the power printed on the objective and the eyepiece — a 40× objective with a 10× eyepiece, not the numbers from a different lens.
What is total magnification?
How much bigger the specimen appears
The total magnification calculator tells you how much larger a specimen appears down a compound light microscope compared with your naked eye. A compound microscope magnifies in two stages: light first passes through the objective lens close to the slide, then through the eyepiece (ocular) you look into. Because each stage magnifies the image the previous one produced, their powers multiply rather than add. The calculator takes the two numbers printed on the lenses — say a 40× objective and a 10× eyepiece — and returns the single figure that describes the whole instrument, here 400×.
Enter the objective magnification and the eyepiece magnification to get the total magnification of your microscope instantly.
Total magnification is the objective magnification multiplied by the eyepiece magnification — never the sum of the two.
Total = objective × eyepieceThe lenses multiply because each one enlarges the image that reaches it. The eyepiece does not magnify the real specimen directly — it magnifies the already-enlarged image formed by the objective. So a 40× objective and a 10× eyepiece give 40 × 10 = 400×, meaning the specimen appears 400 times larger than it would to the unaided eye.
Suppose you have rotated the 40× objective into place and your microscope has the usual 10× eyepiece.
Read the objective power
The number on the objective lens is 40× — the first stage of magnification.
Read the eyepiece power
The eyepiece you look through is marked 10× — the second stage.
Multiply the two
40 × 10 = 400×. The specimen appears 400 times larger than with the naked eye.
The total magnification describes the instrument as a whole, and on a standard school or lab microscope the same 10× eyepiece is usually paired with a turret of objectives. A 4× scanning objective gives 40×, a 10× low-power objective gives 100×, a 40× high-power objective gives 400×, and a 100× oil-immersion objective gives 1000× — the practical ceiling for a light microscope. Switching objectives is therefore the main way you change power: each click of the turret jumps the total magnification by the ratio of the objectives, which is why the image suddenly looks very different. Remember that magnification is a pure ratio with no unit, written with a multiplication sign such as 400×; it tells you how much bigger, not how much detail you can resolve.
The multiplication is exact, but what it tells you is narrower than it first seems.
Light microscopes and the magnification–resolution gap
This formula applies to a compound light microscope, where an objective and an eyepiece magnify in series. It gives magnification only — not resolution, which sets how much detail you can actually see. Past roughly 1000× a light microscope produces empty magnification: a bigger but no sharper image. It also does not describe useful magnification limits or electron microscopes, which work on entirely different principles.