The below image will give you some guidance on how each size compares (rough estimate). Please refer to exact measurements before purchasing to ensure it is the ideal fit for your wall.
The regular (small) size is usually best for table side frames that can be placed on fireplaces, entry/hallway tables, desks etc. This size is popular for gifts!
The M, L and XL sizes are perfect for bringing life to any wall in your home. These can be hung solo or as pairs to fill more space. For my framing tips, click here.