#file size

Kiriska: In general, it doesn't hurt to go bigger, though this is mostly so you can repurpose the art for various applications. If you don't know what you plan to use the art for when you make it, it's better to err on the side of bigger.

However, if you do know what product the art is for, it may be better to just work at 300 dpi at your final dimensions.

The one downside of working bigger than you need is that you may end up putting in detail that won't really show up in the product. If you tend to work at 100% canvas size, but your canvas size is significantly bigger than your end product, a lot of that 100% detail won't show up when it gets printed.

Well right now I’ve only been doing stickers which with file sizes anywhere from 120 KB to 550 KB end up in a rough average ballpark of 2″x 2″ in sticker form (Image dimensions lying in the general ballpark near 600px x 600px)

For images I used to make sigil tshirts and other products (none of which are available anymore for the time being), I received best results with images 3.0 MB to 4.0 MB and dimensions in the ballpark of of 4000px x 4000px. There’s room to play with dimensions for sure, but I wouldn’t recommend going below 3000px. Feel free to go larger as far as file size and dimensions since mine turned out kinda small for my tastes from what I can remember

Kiriska: I don’t use an iPad Pro or Procreate, but.

As long as the program can handle your desired print size at 300+ DPI, the quality should be sufficient. Other limitations are down to personal preference (Procreate apparently has a maximum of 128 layers?), but the primary indicator of print quality is just DPI.

16″x20″ at 300 DPI is a canvas size of 4800 x 6000 pixels. (DPI is just a multiplier.) Preliminary googling suggests Procreate’s maximum canvas size is around 8000 x 8000. If true, you should be fine.

Kiriska: You should check with your charm manufacturer for the file sizes they prefer, or see if they have any templates you can use. Usually 300 dpi is what they want.

Kiriska: You do not lose quality resizing down, so you should be fine to resize larger artwork down to your template size. 

However, you should be aware that extra small details may simply be indistinguishable at a smaller size. A 2in charm cannot hold as much detail as a A4 print -- there just isn’t enough room.