1. Open ImageJ
2. Open picture using ImageJ toolbar
3. Click on the tool that fits the shape of the object you are measuring (ex: line or circle) at the top of the toolbar.
4. Click and drag the tool to outline the object, line, or area you want to measure.
5. Go to analyze and click measure (or after you have used the tool, click ctrl+m to measure).
6. The results box will tell you the length in pixels. If you know the scale, then you can set ImageJ to measure in specified units.
*Set scale if known
- Using the line tool, draw a line across the known length on the picture.
- Click on the analyze button on the toolbar.
- Go down to set measurements.
- Add the known length and units.