Your numbers
Calibrate from
Sensor size and objective magnification
Width of a ruler or stage micrometer across the frame
A measured distance on a stage micrometer photo
Sensor width (mm)
The edge that matches the pixel count below, such as 22.2.
Pixels across that edge
For example 3456.
Objective magnification (×)
Relay or adapter factor (×)
Leave empty for 1. Krebs measured about 2.12.
Millimetres of the scale that fill the frame width
Read this off a photo of a stage micrometer.
Real distance measured (µm)
For example 1000 for 1 mm.
That distance in pixels
Measure it in an image editor.
Width of your exported image (px)
Needed for the stage route. For the others leave it empty unless you resized or cropped.
Scale bar length you want (µm)
Optional. Empty gives a tidy suggestion.
Calculate
Load the worked example
Reset
Result
Fill in the fields and press Calculate.