Are you ordering mats or sized mat boards with your frame order?
If so, go to the Mat tab first and put in your measurements. The calculator will do the calculation to ensure that the size is correct. Then go to the Frame tab and the size will automatically appear so you can order the frame and all other components.
Ordering multiple items with similar specifications? Click "duplicate" under the item listed in the cart that you would like to copy. Edit sizes, finishes, or components, and then click "update."