The most practical formula for calculating on-screen magnification of a digital microscope is:
On-Screen Magnification = (Width of Monitor Screen) / (Width of the Object Spanning the Screen)
Let’s say you want to measure the magnification of your digital microscope setup:
1. Place a ruler (or a stage micrometer) under the microscope. This is your object with a known size.
2. Select your preferred zoom factor and measure the screen width: For example, a 27-inch monitor has a viewable width of about 600 mm. (Physically measure this for accuracy, as the “inch” size is the diagonal).
3. Read the object width: Look at the image. How many millimetres of the ruler are visible across the full screen? Let’s say you see 20 mm of the ruler.
On-Screen Magnification = 600 mm / 20 mm = 30x
This means the image of the object is magnified to appear 30 times larger on your screen than its real-life size at this zoom factor.
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