How much chin improvement is realistic for fillers? i.e. How many mm/cm of projection or width is realistic?

Chin augmentation can be accomplished with fillers or implants, but in my experience, fillers are best for more subtle changes and implants better for a more dramatic change.  I would not consider one centimeter or more of added projection subtle, so my recommendation in your case would be to use an implant.  

Fillers for the use of chin augmentation is not a good option in my opinion. Specifically in your case if you're wanting a centimeter of improvement. Your best options would be to look into either a chin implant or a sliding genioplasty.

Subtle and assymetric improvements of the chin and jawline area are achievable with fillers.  I am interested in where you got the measurements that you are describing. Assumably you did not stand in front of the mirror and come up with these on your own.  If your surgeon told you that this is the amount of forward projection that you need and you find someone to fill you instead you are unlikely to get the same result. You may need to choose between a more subtle result or a more dramatic improvement with an implant and a complete correction. You can also do a filler and see how you like it and later complete a chin implant surgery when the filler disappears if you like.For a cm or more a filler is not the best option, in all liklihood, but every situation is different and is best evaluated by a plastic surgeon who does chin and chin-jawline implants regularly and with good results.Petite jaws often result in the whole face looking off balance and even interfer with you bite and the function of your teeth.  Correction can completely rebalance the face in a positive way that can dramatically change the way people approach you.  You chin also balances you nose and rhinoplasty is sometimes needed to help as well.I hope this helps you weigh your options.  Best of luck.

  Fillers do not work well in the chin area for a significant amount of augmentation, and are only temporary. When patients need 1cm of projection, a  Silastic chin implant is the much better option. Chin implants are manufactured in a variety of sizes and shapes, can be custom carved when necessary, and are placed through a submental approach under local anesthesia as an outpatient surgical procedure. For many examples of chin implants, please see  the link below

  Hi, I have performed many chin augmentations using a dermal filler (Restylane Lyft) or with chin implants for a permanent enhancement.  A chin implant provides better contours and volume versus a dermal filler but that doesn't mean that a dermal filler doesn't work well.  I perform lots of facial implant surgeries but think it's a great idea for patients to try a "well placed" dermal shaping filler first, just to be certain that they want more.  That's what implants offer... more volume and long lasting results.  Hope this helps.  

Its seductive to think that some injections can give you what an implant can. But, it cannot.When you make a pocket for the implant, you detach the skin from the bone creating space for the implant. With injections, into the skin, the skin cannot usually distend significantly. Pull your chin's skin forward. Its doesn't stretch much at all.