just to add to Colin's comments - if you are using this to resize a control, don't forget to to account for margins (if they are being used, default is 0 so you may not be) and border thickness which takes up space inside the stated size of a control
other factor you may want to take into account is there are 15 twips to a pixel - the smallest unit by which a control can be positioned/sized on the screen (will be different for printers which uses DPI (dots per inch, typically 150 for normal resolution, so around 10 twips per dot). So 7200 is 480 pixels. Not sure whether with 7198 (479.87 pixels) would be rounded up or down but I would round whatever value you get returned to the next 15 - so 7201 would be rounded to 7215.