When calling for a quote you will need to have the picture size and mat size you desire for your picture.

When measuring your picture for framing you will need to decide if you want the mat to come all the way into the image or leave a border all the way around.  With a measuring tape, determine the width and height of the image.  Select a mat-- or mats-- within the color range to draw your eye into the picture.  You may also want to consider the colors in the room where the picture is going to be placed, to see if you can coordinate with existing room colors.  Decide how much mat you want to show around the image.  This will give you a frame size you need.

For example:

Say your picture is a 11 x 14 and you have decided to put a 2" mat around it this will make your frame size 15 x 18.  A 3" mat will make your frame size 17 x 20 and so on.

In selecting your mats and frame keep in mind that first you want to frame it for the picture and secondly for the room it will be going in.  Typically your picture outlasts your furniture.   Pick a mat color that enhances the colors in the picture and draws you eye into the image coordinate with a tone of moulding that goes with the mat and time period of the picture and you have created a work of art that anybody would be proud of.