I wish to create digital painting to be printed on canvas. What size do I work on?

Do I work on small size like A4 and stretch the picture or do I work on actual out put size?I wish to create digital painting to be printed on canvas. What size do I work on?
The rule of thumb is that you should work on a digital document opened to the final size of the printed form, and, at the final resolution. Working to canvas means that the resolution need not be as tight as you would for a good print on paper. Where you might otherwise want to design at 300 ppi or finer, much of that resolution would be lost between the threads of the canvas. You can get away with 150 or even lower ppi.





If it's to be an 18 by 24 inch canvas, then design it in an 18 by 24 inch file. (or slightly larger) You don't want to work on file that is any SMALLER than the finished size. What would be the point of introducing any pixelization if you don't need to?





On your MONITOR, of course, you zoom out to an image size that is comfortable for the portion of the image working on. And zoom in for working on finer detail.





Just remember, when it comes to printing, enlarging a small pixel only results in making a larger pixel. If you don't want to see individual pixels, then make them too small to see.I wish to create digital painting to be printed on canvas. What size do I work on?
A lot of the time it's best to work larger than the output size so when it is made smaller the image is sharper.


This is what most professional companies do!
If you're working with vector graphics, any size will do as it will not degrade during resizing. If not, well, I've only ever had success with this kind of project by starting at the final production size.
Jordan M has the right answer


Work larger then reduce to the size you want.