The short and sweet answer is sometime between 4 weeks old and 4 months old. In general, the smaller the ears are, the sooner they will stand up on their own (and vise versa). There are a few odd-balls out there that take longer to stand up and it doesn’t mean there is anything wrong with your puppy! But if you want your Frenchies ears to stand up sooner just tape them up with masking tape. Gently wrap the tape around your puppy’s ear until it is supported. Replace the tape every day or whenever it falls off and check the ear in case irritation occurs. It may take a few days to a few weeks to erect the ear. Do not use any other kind of tape besides masking tape. Masking tape has the perfect amount of stickiness and toughness that will hold the ear up without hurting your puppy when it comes time to remove the tape. Do not try to tape up your puppy’s ear if they are a long-haired breed.
Teething also plays a role in dropping ears. The reasoning behind this is that intense chewing during the teething stage causes the jaw muscles to become tired and weaken. The jaw muscles are connected to the ears and help control how they stand up (just open and close your mouth and few times while paying attention to any movement in your ears and see for yourself!) So after a vigorous chewing session your puppy’s muscles get tired and don’t hold the ear up straight. This will correct itself over time and you don’t have to do anything to help your pup get over the stage. But I do recommend offering your Frenchie a large real raw bone to chew on while supervised. This will keep your puppy from chewing on other things (like your furniture!) and at the same time add calcium and cartilage to his/her diet to promote healthy development of bones, ligaments, tendons, and teeth in your growing puppy.
I hope you found this information helpful. And as always, sending our love and our hugs from NW Frenchies.