In the Measurement group you can change the "Units" from " % of Page" to "inch". You can now set the Left and Top margins of the frame as well as the Width and Height, in inches. You can use the < TAB > key to navigate from one field to the next. When you are done, click on OK.

If you press the <F1> key while the Layer Properties dialog box is open, you will receive context sensitive help about the different properties that can be set in this dialog box.

If you save the Origin Project, all aspects of the graph are saved, including the graph size and fonts used, tick labels, etc. The data in the graph is also saved.

If you wish to save the graph window with all of your formatting, including labels, fonts, and frame size, but without the actual data, you can save it as a graph template. This is done by having the graph window active and selecting:

File: Save Template as… and giving the template a name.

To create a new graph using this template you would select the data from the worksheet as you normally would. From the Origin Menu bar select:

Plot: Template… and select the template you previously created.