I haven't used your profiling software and colorimeter but I guess you want to display an image on your monitor with dimensions equal the dimensions of a real life ruler?
One way to do it is to display the software rulers in Photoshop from View > Rulers, then refer to a real life ruler and using the zoom feature, use trial and error until both rulers match.
The other more intelligent way is to enter the screen resolution of your monitor in the Photoshop Preferences > Units & Rulers > Screen resolution. Then when you choose View > Print Size, the image will be displayed on screen with its software rulers matching real life ruler. Have in mind that you can right click on the Photoshop rulers and change the units. You can set and verify the dimension of your image in spatial units (used for printing) by using Image > Image size > Document Size section > Width and Height. Make sure to use units that you have on your real life ruler and uncheck Resample Image if you just want to check the image size with different spatial units. If you want to change the print size of the image you can do it in two ways, without resampling, just by changing dimensions/ppi relationship or with resampling checked which changes the pixel count of the file by adding or removing pixels.