resize jpg file to a given size in cm

[fpantin]

Hi,

how to resize a jpg file to a given size in centimeters? When I open a 600*600 pixels jpg file (created with the R software) in ImageJ, I try the following:
Analyze > Set Scale...
   - Distance in pixels: 600
   - Known distance: 6
   - Pixel aspect ratio: 1.0
   - Distance in pixels: cm
Then: File > Save As > Jpeg...
in order to get a 6*6 cm jpg file.

However, when I open the new jpg file in Word, the old dimensions are kept (15.92 cm). If I save the file as Tiff, my figure is actually 6 cm in Word. What's wrong with jpg?

Thanks,

Florent