Unfortunately there is no easy way to change the measurement unit for the tools inside the image editor. When it comes to editing images, pixels are the most popular unit because they are not dependent on the DPI of the monitor your application is looked on.
If you want to use inches in the image editor, you can achieve this by creating a custom tool as shown in this demo. Note that you can reuse the built-in ResizeCommand but you will still have to create you own UI control and Tool class that use it.
Please don't hesitate to contact us again if you need more help.
All the best,
the Telerik team
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