Lynn- a couple more things to take into consideration, including above inputs. 1. Do you envision putting any appliances in this space, like a small additional refrigerator; or free standing wine cellar? Make sure whatever door size you decide on the appliance will fit through this doorway with a few inches to spare. 2. Is a pocket door an option? Depending on layout, this can be good solution because you save wall space. 3. How will the door open? Left or right? Is there sufficient wall space to accommodate this swing? 4. Could you use two doors (French door type) to help space management?
If you have space I would put a 36" door. That would accommodate most appliances. Some people are putting antique furniture pieces in pantries, which add interest and save some trim carpenter build out money. Most furniture would be able to fit through 36" door opening. Remember, a 36" door allows around 33" clearance with door frame etc. 33" would allow a standard refrig to fit through too. Need to consider door handles on appliances too. To better advise, I would like floor plan of the kitchen and pantry so I get the full picture. It is all in the "details".