It depends on where you had it done, usually they are done at 14g but may be 16g.
14g is normal for a male lip piercing, 16g is normal for a female lip piercing.
14g to 16g is normal for a male lip piercing, 16g to 18g is normal for a female lip piercing.
18-16 Gauge
Its not just navel piercings that can reject, its all piercings! Its a risk you take when you get the piercing done. Your body simply sees the piercing as a bad thing and pushes it out, You can try again with the piercing but it is not recommended in the same place.
14 gauge is the standard (most commonly used) gauge for belly rings. The thickness of the post that goes through the piercing is measured as 1.6mm in the metric system.
Technically, you could. There is a difference in gauge size though. An eyebrow piercing is a 16 while a belly ring is a 14. It would hurt to move up in size and would probably look unattractive because belly rings have much bigger jewels/ends.
Well I would suggest going to your local professional body piercer and have your piercing stretched up with a taper (don't worry it doesn't hurt) , the average size or gauge is 14g . If your jewellery is 16g or smaller then it's too small for the piercing and can pose a danger of tearing the piercing (something you don't want to happen).
Normal ear piercings are 18 gauge.
It is normal for a lobe piercing to be 16 or 18 gauge... but it is normally 18. A 16 gauge is normally used for tragus piercings :)
Most "normal" piercings are 18 gauge, so yes, I dont see why not.
Every piercing is different, just like people so there is no "normal" piercing size, besides it's hard to tell if you are asking about gauge or depth. Each piercing has a unique size and depth, if you are dealing with a professional body piercer they will handle you accordingly.