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- Activate Ruler tool by Tools > Measurement > Ruler
Draw a line to calibrate on a scale which is found on the image.
Note For more accurate results, it is recommended to use a calibration line as long as possible.
- Right-click on the calibration line, and select Calibrate
- Enter the length of the calibration line in a physical unit as indicated on the scale where the line is drawn, and select OK
The calibration line is shown in a physical unit now, and all other measurements are shown in a physical unit.
Note Measurements can only be calibrated for images individually, so a calibration done for an uncalibrated image does not apply to other uncalibrated images.