Microscope Magnification and Field of View Calculator
Enter your eyepiece, objective and field number to get magnification and field of view.
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Microscope Magnification and Field of View Calculator by TheCalcTools
How the Microscope Magnification and Field of View Calculator works
Total magnification is eyepiece × objective. The field of view diameter is the eyepiece field number divided by the objective magnification.
Estimate a specimen’s size by how much of the field it spans, or divide a measured image size by the magnification.
The formula
Worked example
Using the default values shown in the calculator:
| Eyepiece magnification | 10 |
|---|---|
| Objective magnification | 40 |
| Field number of the eyepiece (mm) | 20 |
| Measured image size (mm, optional) | 2 |
| Specimen spans what fraction of the field | 0.25 |
- 10× × 40× = 400×. Field of view: 20 ÷ 40 = 0.50 mm (500 µm).
Result:
| Total magnification | 400 |
|---|---|
| Field of view diameter (mm) | 0.500 |
| Field of view (µm) | 500 |
| Specimen size from field fraction (µm) | 125.0 |
| Actual size from image size (µm) | 5.0 |
Frequently asked questions
What is a field number?
The diameter in millimetres of the eyepiece’s field stop, often printed on the eyepiece (for example 10×/20 or 10×/22).
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.