Accuracy of line draw tool when using it to set a scale for Image/j

I had a question about the accuracy of the line draw tool. I am conducting an experiment which I measure the displacement of microscopic particles, so I will use the Image/J software to measure the trajectory of each particle. In order to get the distance in millimeters, I must apply a scale, pixels/mm. I can do this by drawing a line on an imagine of a ruler I capture and then using the settings to apply a scale. I want to know what the uncertainty in the pixel measurement is, in other words how accurate is the line in counting pixels and what is the margin of error?

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Hi @Soubhaan_Masood
Welcome to the forum.

Line selections and measurements can be done with subpixel accuracy.

The exact length of the line is shown in the status line.

Note: If you press the SHIFT key during selecting the line the line will be drawn only in the direction 0°, 45° or 90°. This can ease the calibration.

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